The official newsletter of the Thematic Network for Ultraviolet Measurements

Issue 1 / September 1998

Contents 

Editorial

Coordinators Column

The First Workshop in Espoo, March 2 and 3, 1998

Extended Abstracts

Announcing the Second Workshop in Braunschweig, November 9 - 11, 1998

Working Groups

News-Flash

Service Card

Editorial

UVNEWS is the official newsletter of the Thematic Network for Ultraviolet Measurements. The Network is funded by the Standards, Measurements and Testing programme of the Commission of the European Communities, as project number SMT4-PL96-9329.

UVNEWS is published twice a year. It is aimed to exchange knowledge between the participants of the Network and to disseminate information on the forthcoming and past activities of the Network. The newsletter also contains scientific and technical articles on UV measurements and a news-section about activities in the field of UV measurements. The newsletter welcomes all announcements and articles which might be of importance for the readers.

This first issue reports on the progress of the first workshop, which was held in Espoo, Finland, on March 2 - 3, 1998. It also announces the second workshop to be held in Braunschweig, Germany, on November 9 - 11, 1998. To this second workshop, also other institutes than the participants of the Network are welcome at their own expense. The registration forms for the workshop may be found elsewhere in this issue.

Material to be published in UVNEWS should be sent to:

Helsinki University of Technology
Metrology Research Institute
Petri Kärhä
P.O.Box 3000
FIN-02015 HUT, Finland

Telefax: +358 - 9 - 451 2222
E-mail: petri.karha@hut.fi

In case of longer articles or announcements, use of E-mail is preferred.

The second issue of UVNEWS is preliminarily scheduled for March 1999. This issue will include a report of the Braunschweig workshop, and information about the third workshop which will be held at NPL in September 1999. Announcements and possible articles for this issue should be sent to HUT by the end of February.

Petri Kärhä
Editor in Chief

Coordinators Column

The commercial, scientific, and industrial applications of ultraviolet radiation and the consequent need for UV measurements have increased enormously over the last 20 years. Ultraviolet radiation has found application in semiconductor photolitography, material curing, non-destructive testing, acceleration of chemical processes, water purification, sterilisation, phototherapy and solarium appliances. Concerns of the environmental and health effects of solar UV radiation penetrating into the biosphere through the depleted ozone layer have also greatly emphasised the urge for accurate and reliable UV radiometry.

The measurement problems in the UV wavelengths are much more severe than in the visible wavelength range, since both sources and detectors tend to unstable in the UV. However, progress in one field of application of UV radiation should be directly applicable in the other fields.

The Thematic Network is aimed to enhance exchange of results and ideas between the research laboratories and industry and also to obtain a better understanding of the problems associated with the calibration and testing work. To achieve this objective the Thematic Network arranges a series of workshops over a period of three years. It has already been agreed with two research projects that these workshops will be used to disseminate information on the projects and to gather ideas/problems from the user community.

The first workshop in March 1998 identified four key issues and established working groups to study these subjects in more detail. The subjects and contact information of the working group leaders are given on page 23. The Thematic Network will also arrange training courses on UV radiation measurements. This activity is coordinated by the National Physical Laboratory, UK.

To meet the objectives of the Thematic Network an active contribution of all the participants is needed. I am looking forward to seeing you all in the second workshop in Braunschweig!

Erkki Ikonen
Coordinator of the Thematic Network

The First Workshop in Espoo, March 2 and 3, 1998

The first workshop of the Thematic Network for Ultraviolet Measurements was arranged in Espoo, Finland on March 2 and 3, 1998. The number of participants of the workshop was approximately 70.

Nineteen oral presentations were given to form the state-of-art review in UV measurements, and to high-light the existing problems in the field. These presentations were given in four categories: Industrial UV applications and measurements (4 presentations), Measurement standards and calibration methods (7 presentations), Solar UV measurements (5 presentations), and UV measurements related to health and safety (3 presentations).

In addition, 20 posters were presented, and 4 excursions were arranged. The excursions took place at the Measurement observatory of the Finnish Meteorological Institute in Jokioinen, Helsinki University of Technology in Espoo, Radiation and Nuclear Safety Authority, STUK, in Helsinki, and the Finnish Institute for Occupational Health in Helsinki.

The presentations highlighted four key issues within the UV measurement problems. Four working groups were formed to study these problems, and suitable experts were assigned to act as leaders of the working groups. More information about these working groups may be found on page 23 of this issue. It was decided that the coordinator with the leaders of the four working groups will form a steering group for the network. This steering group will make decisions on various practical items of the network.

The principles for selecting new participants to the workshops were agreed. The maximum number of participants was limited to 100. The first priority will be given to new participants from countries with few or no participants at all. The possible new participants will be evaluated by the steering group of the network, which has the authority to select a new participant. So far, 5 organisations have indicated possible interest in joining the network.

With Commission's agreement, the selected new participants may be financed for their travel expenses. Some participants could not attend the first workshop which resulted in savings of approximately 10.000 ECU. In addition, one participant has withdrawn. The savings would allow financing of 5 new participants for the forthcoming three workshops.

David Nettleton of NPL led a discussion about the contents of the training courses which will be arranged by NPL, UK. It was decided that the courses will be aimed for industrial technicians and for scientists new to the field. The training courses are planned for years 1999 and 2000. The courses will be kept at quite basic level. Both theoretical and practical issues will be covered, including e.g. basic radiometry, instrumentation, calibration techniques, measurement practice and uncertainty evaluation.

There was also a long discussion about possible themes for the further workshops, which resulted into several suggestions. The themes for the workshops will be selected later by the steering group of the network.

The workshop also concentrated on several practical issues of the Network, including e.g. contents of the Newsletter and the coming WWW-pages, schedule for the forthcoming workshops, and the need for a Consortium Agreement. A consortium agreement will be made. Drafts of the agreement will be circulated before the November 1998 workshop.

The participants of the first workshop had the possibility to write extended abstracts of their presentations in the first workshop. Ten participants used this opportunity. The extended abstracts sent by the dead-line may be found in the following pages.

Further information about the workshop, including e.g. the minutes of the workshop, is available from the Coordinator.

PK

Extended Abstracts

Measurement of Intense UV-C Radiation

There are important industrial UV applications as for instance photochemical curing of lacquers, colours and plastics, UV oxidation of pollutions or UV synthesis of chemicals where rather high UV irradiances up to several kW per m² are applied to the objects. For optimum process control, such irradiances, mostly in the UV-C, have to be measured quantitatively, mostly continuously over an integral range in the air UV-C, UV-B and/or UV-A. So, detectors should be stable over thousands of hours against intense and hard UV radiation, solar-blind, calibrable and linear also in the high-intensity range and sufficiently responsive over a broad wavelength range.

It is rather difficult to meet such requirements. For stability and linear response, all UV sensors, except for the MI sensors developed by us, need a signal-attenuating coating that itself is affected by hard radiation, humidity and contamination. In order to fit the wavelength range to be measured, optical filters and/or phosphor layers are positioned in front of detectors. However, solarisation, enhanced temperature and humidity strongly influence spectral transmission. Diffusers put in front of sensors do not perform cosine correction equally for all incident wavelengths and sufficiently for angles larger than 60°. With respect to ageing by intense radiant exposure, diffusion type Si pn-photodiodes become unstable under irradiation below 250 nm. Diffusion type np-junction diodes with nitride oxide passivation layer exhibit an increased radiation hardness in the air UV. Best results are obtained with Schottky-barrier diodes and the spatially more uniform PtSi - n-Si diodes, because there is no oxide passivation layer in which traps can be formed by exposure to hard UV. All such sufficiently stable sensors, except for SiC-photodiodes, are not solar-blind, but have highest response in the VIS or IR. SiC-diodes have the disadvantage of rather small, not very uniform sensitive area.

We have tried to develop some alternatives with respect to the state of art. Phototubes were made with bulb of glass, for instance Vycor, that has the right cut-off wavelength and has been pre-aged under strong UV. For the air UV, Sn and Au have proved as rather stable coatings of the photocathode. Under very intense UV-C, they need an attenuating PTFE diffuser in front.

Photoelectric MI sensors have been made of metal-coated insulators. The semitransparent front layer of Al, Cu, Cr, Au or Pt forms the photocathode. The thin insulating semiconductor, for instance sapphire or magnesium oxide, determines the wavelength onset of responsivity at about . The opaque metal back layer gives the anode. A voltage of a few hundred volts is applied across the insulator. In contrast to Schottky diodes, the metal coating generates an accumulation layer at the MI interface. An UV-C exposure of 750 kJ/m² (by xenon short arc) produced a responsivity decrease of less than 3 % of the initial value.

Another problem associated with the measurement of intense UV-C radiation is the calibration of spectral detector responsivity, because there are no transfer standards, neither lamp nor detector standards, available for such high UV-C irradiances.

Proposal for Industrial UV-Radiometry

Scope of the proposal

It is well known that measurements of UV-radiation can be performed with spectral and integral methods. With the spectroradiometry, highly accurate and resoluble measuring results can be achieved, which are necessary for scientific documentation. However, spectroradiometers with acceptable quality are cost- and service-intensive and require qualified technicians.

Measuring equipment according to the integral method generally are portable (hand held), battery-powered, mostly payable and usable for high-speed signals, if they are equipped with suitable electronics. Beside this, there are some problems with such measuring equipment:

• Up to last two years, existing integral UV-meters are not accurate,
• There is not a common internationally accepted standard characterising and classifying UV-meters into different classes corresponding to different UV-measuring tasks.

These problems are to be overcome in the next future.

Existing guidelines for characterising radiometers and photometers of integral method

Up to now, following guidelines are worked out:

1. CIE Publication No. 53, 1982: "Methods of characterising the performance of radiometers and photometers,"
2. German standard 5032 - part 6 (only for V()-photometers): "Photometry, photometers, concept characteristics and their designation,"
3. German standard 5032 - part 7 (only for V()-photometers): "Photometry, classification of illuminance and luminance meters."

Papers 1. and 2. defined all uncertainties associated with radiometer heads and display units, among them the spectral matching uncertainty, the directional response according to cosine-law and the modulated radiation. Based on German standard 5032-6, an European Standard for photometers is under development.

Recommendations for future works in the industrial UV-radiometry

It is recommended to carry out developments of an European Standard classifying UV-radiometers with participation of instrument manufacturers and national standard institutes. Instrument manufacturers should indicate in their product documents the uncertainty limits of UV-meters for different types of uncertainties. Furthermore, from practical point of view, organisation of some workshops comparing the uncertainties of UV-meters of different manufacturers with discussions on suitable calibration methods and standards should be recommended.

UV-Calibrations for Spectral Irradiance and Spectral Responsivity and Their Uncertainties

Introduction

Today, Gigahertz-Optik Company has the only German calibration laboratory for radiant quantities in a wide wavelength range from UV up to IR in the frame of the German calibration Service (Deutscher Kalibrierdienst = German Calibration Service). DKD-laboratories are accredited and supervised in Germany by the Physikalisch-Technische Bundesanstalt (PTB). The German Calibration Service is the member of the EAL (European Cooperation for Accreditation of Laboratories). The aim of the EAL is the establishment of an European base of mutual acceptance of calibration certificates issued by the laboratories accredited by EAL-members.

DKD-calibration for the spectral irradiance

Generally, the calibration of the spectral irradiance can be carried out by comparing the output signals of a suitable double-monochromator setup delivered by the lamp to be calibrated and the standard lamp under the same irradiation conditions. The calibration arrangement in the DKD-laboratory consists of a movable table containing the standard lamps and the lamp to be calibrated, input optics putting the radiation of standard and calibrated lamps onto input slit of the double-monochromator, a double-monochromator strongly reducing the stray light, different detectors for calibrations between 250 nm and 2500 nm, a data acquisition system with measuring and system controlling software. With this software, photosignals of the detector can be evaluated for determining the absolute spectral irradiances.

The DKD-laboratory of Gigahertz-Optik Company uses as standard lamps for spectral irradiance in UV-range 1000 W halogen incandescent lamps of FEL-type. The FEL-lamps of OSRAM/ SYLVANIA were carefully tested by PTB and are suitable for calibration purposes in UV-ranges from 250 nm. For the PTB-standard lamps, used for DKD-calibration purposes, an uncertainty of 0,001 µW cm^­2 nm^­1 for  = 250 and 260 nm and 3 % for 270 nm <  < 400 nm are estimated. The transfer uncertainty in the DKD-laboratory can be estimated to be 1 % resulting into a DKD-uncertainty of 4 % between 270 nm and 400 nm.

The calibration of the spectral responsivity

The spectral setup for the calibration of the spectral responsivity of detectors is generally the same for the calibration of the spectral irradiance. The DKD-standard detectors, together with the photocurrent meter, are calibrated by PTB. They are silicon detectors (HAMAMATSU S1337-1010 BQ) with quartz window. Their inside temperature is measured with PT100-resistance. According to investigations of PTB and NPL (UK), these detectors have a shunt impedance of about 2 G yielding a linearity of better than 0,05 % over 6 decades and an ageing rate of better than 0,3 % per annum between 250 nm and 1000 nm. PTB gives a relative uncertainty of 0,7 % at 248,3 nm and 0,5 % for all other UV-wavelengths and an additional absolute uncertainty of about 0,4 %. At the DKD-wavelengths up to 366 nm, an uncertainty of 3 % and for calibrations at 380 nm and 400 nm, an uncertainty of 2 % can be estimated.

References:

[1] PTB- Calibration certificate No. 41352-PTB-95 ( 03.08.1995)

[2] PTB- Calibration certificate No. 9111-PTB-97 ( 28.05.1997)

UV-Health Hazard Assessment - Guidelines, Measuring Methods and Equipment

With the strong depletion of the stratospherical ozone layer and consequently overproportional increasing of UV-B-radiation on the earth surface and with new application fields of ultraviolet radiation in medicine, biology, chemistry and industrial manufacturing processes, there is an urgent need to recognise and assess the potential radiate health hazards as well on the indoor as on the outdoor workplaces.

Generally, actinic effects can be divided into effects on the human skin (erythema, DNA, non-melanoma-skin cancer) and effects on the human eye (photoconjunctivitis, photoceratitis) and the general health damage on work places (ACGIH-actinic spectrum).

In the last 15 years, a number of international and national institutions have recommended relevant actinic functions being able to describe the UV-health damages on work places and Maximum Permissible Exposures (MPE) for occupational and public exposure to UV-radiation. All guidelines have recommendation character. Among them, the following two guidelines are mostly used:

• American Conference of Governmental Industrial Hygienists, ACGIH: "Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposures Indices," Cincinnati, 1995
• IRPA/ICNIRC: "Guidelines on limits of exposure to ultraviolet radiation of wavelengths between 180 nm and 400 nm" (1985 & 1989)

For the assessments of UV-health damages, a general health damages function was defined. This ACGIH-function describes the spectral effectiveness of UV-radiation on human skin and eye. The well-known UV-erythema function was defined for the skin reddening caused by UV-radiation and the threshold dose for sensitive skin type should be 250 J/m². Today, these functions are objects of intensive discussions on long-term effects of UV-radiation (person-dosimetry).

For health damage assessments, two measuring methods can be used:

• Spectral methods: measurements of the spectral quantities to be needed [e.g. spectral irradiance E_e() or spectral radiance L_e()], evaluation with the action spectrum s()_biol,rel to be observed and integrating this product.
• Integral methods: measurements of actinic radiant quantities can be done with "radiometers for the measurements of actinic radiant quantities," using a radiometer head with a relative spectral responsivity s()_rel, which is spectrally matched to the action spectrum of the considered effect.

Recently, Gigahertz-Optik has developed the radiometerheads spectrally matching the ACGIH- and erythema-functions from 220 nm up to 400 nm. The uncertainty of cosine-response is better than ±5 % for incidence angles up to 60°. With the laboratory equipment, it is possible to measure fast changing radiation intensity (welding arcs, flash lamps, pulsed lasers…) up to 10 MHz.

For hand-held and laboratory measuring devices, the dose function is integrated. The devices are calibrated in the laboratory of the German Calibration Services.

Filter Radiometry Based on Direct Utilisation of Trap Detectors

We have developed a new type of filter radiometer, comprising of a reflection trap detector, radiometric aperture and a set of temperature-controlled band-pass filters. The construction of the filter radiometer is presented in Figure 1. The temperature controller has been realised in a way that allows fast and reliable changing of the filters, without altering the alignment or contaminating the filters.

Due to the low reflectance of the trap detector, all the components forming the filter radiometer may be characterised separately. This is a significant advantage, as it allows the use of the most suitable instruments for all characterisations. The spectral responsivity of the trap detector is determined with the aid of a cryogenic radiometer. A high-accuracy reference spectrometer is used in the characterisation of the filters. The area of the limiting aperture is measured by using a novel laser-based method.

The filter radiometer has been successfully used in several applications, including a high-accuracy luminous intensity scale and a spectral irradiance scale in the 300-900 nm range. The spectral irradiance scale has been recently compared with a 1-kW spectral irradiance standard lamp that has a calibration traceable to NIST. This intercomparison indicates that in the UV region between 300 and 400 nm, the scales of NIST and HUT agree within 1 %.

Monitoring UV Irradiances; Quality Control and Cosine Correction

The main goal of the RIVM UV-monitoring program is to determine long-term trends in the UV climate. An UV monitoring system has been designed and built and is operational since '93. The system consists of a spectroradiometer, Robertson-Berger SL 501 biometers and pyranometers. The system is built in a light-tight and temperature stabilised mobile container. In the monitoring routine measurements are performed every 12 minutes from sunrise to sunset. The measurements are used for monitoring and validation of atmospheric UV transfer models, to obtain a tool for estimating past and future trends.

We have developed techniques to use the Fraunhofer structure in the solar spectrum to provide a high accuracy wavelength alignment, and to correct for slit function differences by means of deconvolution. Application provides a tool for the Quality Assurance of wavelength alignment in routine monitoring. The wavelength alignment technique has been extended, improved and extensively tested to enable wavelength dependent shift determinations in the UV-B region of the spectrum and to increase the efficiency of the calculations to facilitate application in routine monitoring. The methods were thusfar applied on over 30 different instruments during large scale international intercomparison campaigns. The accuracy of the alignment method is 0,01-0,03 nm for instruments with slit functions with a FWHM around or below 1 nm. The repeatability is around 0,01 nm. Larger uncertainties can occur if the FWHM of the instruments is considerably higher, and for very low solar angles.

We also have developed a cosine correction method for UV spectral measurements which is applicable not only under clear sky or solid overcast conditions, but also under a variable cloud cover, i.e. for routine monitoring data. Many UV spectrometers are equipped with a diffuser plate to measure solar UV irradiances with non-ideal angular responses. A "cosine correction" should be made to account for this error. In order to perform this correction, the angular distribution of the irradiation on the diffuser plate should be known, i.e. the ratio of direct to diffuse irradiation in first approximation. Our method provides a protocol for clear sky and all cloudy situations and is based on three steps:

1. The measured global irradiance, determines together with the expected level the reduction of the global irradiation by clouds or aerosols. This measured reduction of the global irradiation is translated to an optical thickness of the clouds.
2. A modelled direct to diffuse ratio for clear sky conditions is modified for the overcast condition using the derived optical thickness in step 1.
3. Using these modified values of direct and diffuse irradiance, the cosine correction factor is calculated.

The knowledge necessary for evaluating step 1 is based on Monte Carlo simulations of the total transmission as a function of optical thickness and angle of incidence. In step 2, a standard atmosphere is used with a fixed value for the ozone column and a low aerosol concentration to estimate the clear sky direct to diffuse ratio. This is sufficient for our purpose. We have investigated also the impact on the cosine correction of an anisotropic distribution of diffuse light emerging from the sky or clouds. Generally, it reduces the cosine correction.

Measurement of the Erythemal Effective Dose Caused by UV-B and UV-A with a Detector Film (Biochip VioSpor^â).

For the first time, a detector film has been manufactured which can be used for dose measurements of biologically weighted solar radiation (CIE-MED) as well as for artificial lamps (solaria). Two examples are given to illustrate the effectiveness of the UV-B as well as of the UV-A spectral region in solar radiation and artificial lamps. These data underline the importance of correct measurements in the UV-B and also in the UV-A spectral region.

For the measurement of solar radiation, the detector system has to be optimised in the UV-B spectral region. At high solar elevation angles, the UV-A contributes only a minor part to the total erythemal effectiveness of solar radiation. In the given example UV-A (315-400) contributes 23 % of the total erythemal irradiation.

At lower solar elevation angles and for many artificial lamps, the UV-A part of the spectrum contributes to a high extent to the total erythemal effectiveness. Under these conditions it is very important that a broadband detector gives reliable results not only in the UV-B but also in the UV-A. The given example of a medical lamp illustrates that in this case UV-A contributes 47 % of the total erythemal radiation.

Determination of the Erythemal Solar Radiation and Spectral Characterisations of Various UV Radiation Sources Using the Biochip VioSpor^â - a New UV-Detection Film System

The detector film VioSpor® (spore film; biochip) was tested in several field campaigns. The spore film data (given as daily dose in CIE-MED) were compared with data (given as daily MED dose) deduced from spectroradiometric measurements with a Brewer instrument.

1 MED (CIE) = 250 J/m²

The VioSpor system includes a filter system. Various spectral measurements are done during one exposure experiment. One of the determined values gives the erythemal dose (MED) and the other are necessary for the spectral characterisation of the UV source. The ratio of the various values enable the determination of l_ER. This value is defined as the wavelength where 50 % of the total erythemal effectiveness is caused by longer and by shorter wavelengths respectively. Three examples shall underline the potential of spectral characterisations with VioSpor.

Improved Cosine Diffuser for UV-Measurements

Since the end of last year we are working at the Institute of Medical Physics on a UV-diffuser. The reason for this time consuming undertaking was the inadequate cosine response of all available diffusers. The design is finished and the diffuser is now produced in a small series.

Results:

• deviation of the angular response from the ideal cosine < ±3 % for 0-75° zenith angle
• angular response: spectrally flat
• integral cosine error (DIN 5032) < 2,5 %
• azimuthal error negligible
• designed for use with quartz fibre only
• transmission comparable to transmission of a 1,1mm thick Teflon sheet
• material: Teflon
• housing: protected aluminium, waterproof, polished quartz dome
• production: computer controlled milling machine

Announcing the Second Workshop in Braunschweig,
November 9 - 11, 1998

Introduction

The 2^nd Workshop of the Thematic Network for UV Measurements will be arranged at the PTB, Braunschweig, Germany, on November 9 - 11, 1998. The 2^nd Workshop is not restricted to the participants of the UV Network only. Others may participate at their own expense. All participants are requested to register by sending the registration form to PTB by October 1.

Please notice that the programme starts with parallel sessions of the working groups. If you belong to more than one working groups, you may only attend one. Please notify Werner Möller about which session you would like to attend by E-mail or fax, if you have already sent the registration forms!

Preliminary Programme

Monday, November 9^th, 1998

08:30 Registration (Vieweg Building)

09:15 Parallel meetings of the 4 working groups (Vieweg-Building).
Meetings end at 11:30-12:30

11:30 Lunch and change to the lecture hall (Kohlrausch-Building).
Lunch starts flexibly at 11:30-12:30

13:30 Opening and welcome by the President of the PTB

13:45 General network activities described by Erkki Ikonen and Petri Kärhä (including minutes of the first meeting, consortium agreement, new participants, training courses, www pages, newsletter,...)

15:00 Report *) by the WG1

15:45 Coffee break

16:15 Reports *) by the WG2 and WG3

17:45 Short break

18:00 Report *) by the WG4

18:45 Transportation to the hotels in the city

20:00 Dinner (in the city)

Tuesday, November 10^th, 1998

08:30 2-3 selected presentations *) by WG1 members and discussion

09:45 2-3 selected presentations *) by WG2 members and discussion

11:00 Coffee break

11:15 2-3 selected presentations *) by WG3 members and discussion

12:30 Lunch

13:30 2-3 selected presentations *) by WG4 members and discussion

14:45 Summary/discussion on the theme "Improving the accuracy of UV radiation measurements" (A new EU project)

15:15 Coffee break and preparation of poster session

15:45 Poster session (including exhibition)

18:15 Final discussion (including programme of the next workshop)

*) selected presentations and reports should cover uncertainty problems

Wednesday, November 11^th, 1998

09:00 Visits to different laboratories of the Optics Division, PTB, covering the following subjects: blackbody standard source; photometry; clean-room centre including cryogenic radiometer, solar cell calibration; atomic clocks; length and frequency; characterisation of CCD cameras; and/or optical linewidth measurements

09:00 Final meeting and discussion of the UV Network steering group including the leaders of the working groups

Presentations

The oral presentations are selected by the working groups. In case you would like to have an oral presentation, please contact the leader of the corresponding working group. The list of the working groups with the contact information of their leaders may be found on page 23 of this issue. If you wish to present a poster or exhibit UV measurement equipment, please inform Werner Möller (PTB) about this.

If your presentation (either oral or poster) is accepted, you are kindly requested to send a short abstract of the presentation to Petri Kärhä (contact information on page 3), preferably in electrical form. These abstracts will be distributed to the participants of the workshop.

Venue

The Physikalisch-Technische Bundesanstalt (PTB) is located northwest of Braunschweig (Germany). You can reach Braunschweig by plane (airport Hanover, about 70 km to Braunschweig), by train or by car. There is a public bus connection between the main railway station and the PTB (route 11; it is noted that not every bus of this route will stop at the PTB). There is a public shuttle bus connection between airport and the Hanover railway station. A private shuttle bus connection between the airport and Braunschweig can be arranged by the 'Braunschweig Congress Service'. A reservation form of this service is enclosed in this UVNEWS.

More detailed information about the locations and connections will be sent to registered participants before the workshop. You will find information about Braunschweig in the internet under:

http://www.braunschweig.de

http://www.bs-net.de

Accommodation

The accommodation is arranged by the 'Braunschweig Congress Service'. A number of rooms are already reserved in two hotels of different categories. A hotel reservation form is enclosed in this UVNEWS. You should send the filled form by fax directly to the 'Congress Service'. A private reservation of a hotel is of course possible. You can get the complete information about hotels, prices, and contacts by internet address:

http://www.braunschweig.de/eng/touristik/touristik.fset

Workshop Fee

The participants themselves of the UV Network project (about 60 persons) are invited to attend the workshop without paying a participation fee. Accompanying persons and guests have to pay a workshop fee of 100,-- DM. This fee is paid with the registration at PTB. The participation fee covers the costs of lunch on Monday and Tuesday and the evening dinner on Monday.

Local Organizers

The local arrangements of this workshop will be organized by the department 'Light and Radiation' of the Physikalisch-Technische Bundesanstalt:

Physikalisch-Technische Bundesanstalt
Light and Radiation
Bundesallee 100
D38116 Braunschweig, Germany

Telephone: ++49-531-592-0
Telefax: ++49-531-592-4105
Internet: http://www.ptb.de

Contact Persons for the 2^nd Workshop:

Working Groups

The Network has four working groups, each working on a selected key issue in UV measurements. The working groups are operating mainly by exchanging E-mail. If you wish to join a working group or be informed about its activity, please contact the corresponding working group leader. You may also use the service card at the end of this UVNEWS.

Working group 1: Guidance for UV power meter classification for particular applications

Gigahertz-Optik
Director Anton Gugg-Helminger
Fischerstrasse 4
D-82178 Puchheim, Germany

+49-89-89015920
Fax: +49-89-89015950
a.gugg-helminger@go-puchheim.de

Working group 2: Improvement of measurement and calibration methods for spectrally resolved UV measurements

Physikalisch-Technische Bundesanstalt
Department 4.1 Light and Radiation
Prof. Dr. Jürgen Metzdorf
Bundesallee 100
D-38116 Braunschweig, Germany

+49-531-5924100
Fax: +49-531-5924105
Juergen.Metzdorf@ptb.de

Working group 3: Improvement of measurement and calibration methods for spectrally weighted UV measurements

NPL Management LTD
National Physical Laboratory
Dr. Nigel Fox
Queens Road, Teddington
Middlesex, TW11 OLW, United Kingdom

+44-181-9436825
Fax: +44-181-9436935
npf@newton.npl.co.uk

Working group 4: UV Measurements related to health and safety

University of Dundee
The Photobiology Unit
Dr. Harry Moseley
Ninewells Hospital & Medical School
DDI 9S4, United Kingdom

+44-1382-632240 / +44-1382-633894
Fax: +44-1382-646047
H.Moseley@dundee.ac.uk

The presentations for the second workshop will be selected mainly by the working groups. So if you have results which you think might be discussed in the workshop, please contact the leader of the working group, whose topic best describes your findings.

News-Flash

Symposium: "Solar Ultraviolet Radiation"

Convener: Alkiviadis Bais

Co-Convener: Peter Koepke

Topics for presentations:

1. Analysis of UV observations: (Spatial and temporal variability of solar UV radiation received at the ground, long-term changes from observations with the aid of theoretical calculations).

2. UV Instrumentation: (Developments for the improvement of the quality of spectral or broadband solar UV measurements, advanced calibration methodologies, QA/QC procedures, evaluation of instruments, intercomparisons, instrument characterizations, and data management).

3. UV relations to atmospheric processes: (Relations between UV radiation and various atmospheric parameters, such as clouds, ozone, aerosols, etc., the role of UV radiation in atmospheric chemistry and other atmospheric processes).

4. UV modeling: (Developments of radiative transfer modeling, their validation with actual measurements, dependence of model results on various parameters like aerosols, albedo, scattering, geometry, etc).

5. UV-B forecasting: (Procedures for the UV Index forecasting, in connection to methodologies for predicting the total ozone and clouds, uncertainties introduced by the input parameters, validations of forecasts with real data, biological effects of solar UV radiation, relevant protection measures, effectiveness of public awareness programs).

Further Information:

http://www.copernicus.org/EGS/EGS.html

UVB Instrumentation and Applications provides an excellent summary of the subject of solar UV measurement for anyone involved in, or contemplating, measuring the UV part of the solar spectrum. The book is addressed predominantly to the newcomer to this expanding area of environmental measurement, but contains sufficient detail and practical information to be a valuable reference for the more experienced worker. The practical considerations of solar UV measurement are clearly described, and the book explores the current state of the art of UV monitoring, explained by the historical demand for data. The many applications of solar UV data are discussed and the importance of making appropriate measurements and collecting sufficient supporting data for the analyses required of these applications is highlighted.

Students and researchers in the atmospheric sciences and the photobiology community will benefit both from the UV specific information and the more general advice about data collection which could equally well be applied to other areas of investigation. Anyone charged with measuring solar UV radiation, or understanding the resulting data, will find UVB Instrumentation and Applications extremely useful.

ISBN 90-5699-121-3
Gordon and Breach Science Publishers

Further information:

Dr. Ann R.Webb
Department of Physics
UMIST, P.O.Box 88
Manchester, M60 1QD, UK

With the increasing concern about the harmful effects of UV radiation, CEN/TC 248 has established a new working group, CEN/TC 248 WG 14 "UV protective properties of textiles," to work on a new standard for the determination of the UV protective properties of textile materials. This working group is composed of a number experts from UK, Germany, Finland, France, Italy, Switzerland and Belgium and is working on a new European Standard entitled "Apparel fabrics - Solar UV protective properties - Method of test." The new standard specifies a method for the determination of the erythemally weighted ultraviolet radiation transmittance of standard conditioned appareal fabrics. The method is suited for materials under relaxed and stretched conditions.

The publication for public enquiry of the new standard is expected within the next year.

Further information:

Jan Laperre
Convenor CEN/TC 248 WG 14
Centexbel
Technologie park 7
9052 Zwijnaarde
Belgium

The DG XII of the European Commission and the Finnish Meteorological Institute (FMI) organised an international conference on atmospheric UV radiation in Helsinki on June 29 - July 2, 1998. The conference was also supported financially by COST-713 and the Academy of Finland.

More than 150 scientists from all around the world took part in the conference, which was first of its kind. Newest results on UV research were presented. The general themes of the ECUV conference focused on atmospheric UV radiation and its measurement and modelling methodologies. The following specific topics were included:

• Methodologies for UV radiation measurements (physical and biological methodologies, calibration and characterisation methods and results of instrument inter-comparisons),
• Spaceborn methodologies for estimating UV irradiance,
• Factors affecting UV radiation (ozone, albedo, clouds, aerosols, etc.),
• Past and future UV estimates,
• Radiative transfer modelling of UV radiation, and
• UV forecasting.

The ECUV conference provided an opportunity to present results achieved in the ongoing research projects of the European Commission Environment and Climate Programme, COST-713 project as well as those obtained in national research programmes. The proceedings of the ECUV will be published in a special issue of Journal of Geophysical Research which is scheduled for October 1999.

Further information:

Dr. Petteri Taalas,
E-mail: petteri.taalas@fmi.fi
Phone: +358 - 9 - 1929 4150

http://www.ozone.fmi.fi/ECUV

A new Europe wide project, partly funded by the European Commission, will investigate detectors, optical components and UV measurement methodology with the objective of improving the accuracy of ultraviolet radiation measurement. National Measurement Institutes (NMIs) and industrial companies from France, Germany, Finland, The Netherlands and the UK will all be partners in this enterprise which will be co-ordinated by the National Physical Laboratory in the UK. The project will aim to reduce the UV measurement uncertainty from the underpinning UV base scales held at NMIs to the measurements of UV radiation made by industry and other members of the European UV measurement community. This will be achieved through a co-ordinated programme of work which utilises the experience and specialist facilities available in national measurement institutes across Europe.

The project comprises four distinct areas of research. Two of these are concerned with reducing the uncertainty in base UV scales and hence improving the accuracy of calibrations provided by NMIs. The final two areas are targeted at particular applications in industrial and environmental areas. The first specific area the project will target is the development and evaluation of new types of ultraviolet filter radiometer for the measurement of the spectral irradiance of ultraviolet sources. In the visible region of the spectrum filter radiometers have been developed that can measure the spectral irradiance of a source with an accuracy of less than 0,1 %. These techniques will be applied to filter radiometers in the UV spectral region with the objective of achieving a target accuracy of 0,1 % to 1 %. Work will also be undertaken to investigate the agreement in UV filter radiometer calibration between different NMIs and for different calibration techniques.

The establishment and comparison of ultraviolet spectral responsivity scales based on cryogenic radiometers is the second area that will be investigated. Three different measurement techniques will be compared and evaluated. The target is to achieve an accuracy of between 0,1 % and 0,3 %. One of the main goals of this part of the work programme is to investigate and select suitable detectors to act as spectral responsivity transfer standards for use in the ultraviolet.

Industrial measurement of intense UV irradiance is the third area this project aims to improve. The objective is to develop and evaluate an intense UV irradiance meter. This device will be used for the measurement of the intense UV sources used for industrial applications such as photolithography of semiconductors. The research and development process will involve the utilisation of knowledge gained in other parts of the project and the investigation of the stability of components when exposed to intense UV radiation. The target is to achieve uncertainties of less than 2 % in an industrial environment.

The final aspect of the project is to construct a portable calibrator for solar ultraviolet monitoring spectroradiometers, applying the technology and developments described above. The target is to achieve an accuracy for calibrations in-the-field of better than 4 %.

Consultation and dissemination of results to the European UV measurement community is a cornerstone of this project. Comments and discussion of the goals of this project are therefore welcome.

Further information:

Dr. N. J. Harrison
National Physical Laboratory (NPL)
Queens Rd
Teddington Middlesex
TW11 0LW, UK

Phone: +44 (0)181 943 6443
Fax: +44 (0)181 943 6935
E-mail: neil.harrison@npl.co.uk

The Agreed EUROMET Project "Evaluation of the radiometric performance of UV photodetectors" was established in 1997 as a result of the first "International workshop on detector-based UV radiometry" organised by PTB. Combining the measurement capabilities of NIST, NPL, NMi-VSL, and PTB to investigate the suitability of different types of photodiodes for use as UV detector, a major goal of this international cooperation is to identify candidates for the construction of transfer detector standards to be employed in future programs, such as the EC-funded improved UV scales R&D project and the CCPR key comparison of UV spectral responsivity.

To monitor the progress of the work and to communicate the results to others, the cooperation is accompanied by a series of annual workshops on detector-based UV radiometry. In order to save travel expenditures, the workshops will be organised as satellite meetings of conferences on related matters, such as the kick-off meeting of the new EC SM&T program in Brussels in October 1998 (date and location to be confirmed) or the 1999 NEWRAD conference. In the year 2000 there shall be a joint workshop with the UV thematic network and the EC SM&T program. At the start of the collaboration, silicon Schottky-type photodiodes with a platinumsilicide front electrode (PtSi-n-Si) - developed at the Swiss Federal Institute of Technology - seemed to be the only promising candidate due to their outstanding stability of the spectral responsivity under prolonged UV exposure. PTB as the pilot laboratory financed the production of a mask for 10 mm10 mm active area PtSi-n-Si photodiodes and purchased the devices to be used in the EUROMET project. Each partner was provided with three pristine samples and two specimens calibrated by PTB in the 200 nm to 400 nm spectral range. After the investigations by the partner institutes, that are still in progress, the photodiodes shall be returned to PTB for re-characterisation. Recently, a potential alternative candidate has become available consisting of a commercial diffusion-type silicon n-p photodiode, in which the oxide passivation layer was replaced with a thin PtSi film. First investigations by NIST and PTB indicate that this kind of photodiode has a lower dark current than the PtSi-n-Si Schottky diodes, but a significantly greater spatial nonuniformity.

The current status of the EUROMET project will be reported by the coordinator to the forthcoming second workshop of the UV Thematic Network at Braunschweig in November 1998.

Further information:

Dr. Hans Rabus
Physikalisch-Technische Bundesanstalt (PTB)
Abbestraße 2-12
D-10587 Berlin, Germany

Phone: +49 30 82004-236
Fax: +49 30 82004-238
E-mail: Hans.Rabus@PTB.De (In case of problems try: Rabus@Exp.BESSY.De)

Bentham is undertaking two projects, which are aimed at improving the performance of their spectroradiometers. In the first project, a new stepping motor drive is integrated into the DM150 monochromator, which is used in the temperature controlled UV spectroradiometers. The new drive will have significantly lower power dissipation, which should allow the system to withstand a higher ambient temperature without loosing internal stabilisation. The new product will be available in the next few months.

The second project involves a novel approach to the entrance optics required for global irradiance measurements. The failure of existing diffusers and integrating spheres to follow the cosine law is now considered as one of the major sources of errors in these measurements. Bentham is working on a new, diffuser based device, which already shows an improvement over their D5. The new device should be available in approximately 6 months time.

Further information:

Bentham Instruments ltd.
Geoff Hammond
2 Boulton Road
Reading Berkshire
RG2 ONH, UK

Phone: +44-118-975155
Fax: +44-118-9312971
E-mail: gahammond@bentham.co.uk

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