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European Laboratory for Particle Physics

News from CERN

Manfred Hoefert (with a special contribution by Marco Silari)
The topic of quality assurance (QA) in radiation protection suddenly sprung up in Europe. In a recent talk dealing with the subject we learned that in the States more then 90% of all enterprises are ISO 9000 certified while here on the Continent the figure is less than 50%. While we all strive for quality in our daily work the ISO certification procedure is heavy and loaded with paperwork such that it needs additional and moreso specialized staff. As everywhere also at CERN staff figures are run down such that we in Radiation Protection cannot envisage the full procedure (Remember: Dogbert sticking the label Coffee Machine on the very instrument). Nevertheless the Group has started in the direction of QA looking carefully into what already existed and what was formerly called Complementary Documents (CD) to our Radiation Safety Manual.

These CDs, originally we had only 9, are now called Radiation Protection Procedures (PRP). In the meantime they have reached an impressive 20 and cover subjects like individual dosimetry, access into special radiation areas, expedition of radioactive material, use of instruments. All are presently revised and made into a form coming close to ISO 9000 documents with the name of a responsible person and the date of next revision shown. By the end of the year the work should have been finished with the total number of PRPs possibly having reached 30. I consider this documentation particularly important in the light of a wave of retirements that will hit RP in the coming years when all the expertise that is not well written down will be lost. It would be interesting to know how other labs deal with the issue of quality assurance and passing on expertise.

And since I am speaking of the new generation: Dr. Doris Forkel-Wirth now moved to the RP premises and will work closely with Jan Tuyn whom she will replace in the beginning of 1998.

Following our efforts in Switzerland before the summer the "sales campaign" for CERN's LHC will start again on 20 October with a presentation and an exhibition of the new project in the French commune of Cessy. Following a rough public debate on French television on 4 October about the nuclear issue in France we shall go there with somewhat mixed feelings. In fact, one of CERN's former collaborators stricken by cancer was presented as a victim of nuclear power on this extremely popular show and confronted with George Charpak, the latter being shouted down by the mostly antinuclear audience.

So it happened, what we have always feared and fought, that CERN was placed in the same basket with the nuclear lobby in spite of the fact that our name had long been changed from European Centre for Nuclear Research to European Laboratory for Particle Physics.

Marco sent me the following contribution:

Since 1995, measurements of synchrotron radiation (SR) in the LEP tunnel are regularly carried out at each new value of the LEP energy. This measurement campaign, also asked for by the French INB authorities, will last until next year when LEP will reach about 97 GeV beam energy. In the course of this program, an investigation on the radiation level around the polarization wigglers was carried out during the 80.5 GeV and 86 GeV runs of last year.

Calculations have suggested that the superposition of the SR fans emitted by the set of three wigglers that are installed at both sides of interaction points 3 and 7, results in well localized peaks where a high doses are locally deposited. The position of these peaks is a function of the beam energy. This local concentration of SR may induce localized thermal stresses in the water-cooled aluminum vacuum chamber. To verify experimentally the predictions, measurements were carried out along the vacuum chamber in the proximity of the wiggler units. Integrated dose measurements were performed with alanine dosimetry during the 80 GeV run; additional measurements were carried out at 86 GeV with a Geiger-Mueller counter installed on a robot moving in the tunnel. The latter were made at three specific energies (22, 45 and 86 GeV) by operating the robot for limited periods of time under well defined beam conditions.

From the results of the measurements the predicted well-localized deposition of synchrotron radiation power in the aluminium vacuum chamber of LEP around the polarization wigglers was not confirmed. Although no direct comparison can be made between predictions (linear power density deposited in the vacuum chamber) and measurements (integrated dose or dose rate measured alongside the vacuum chamber), the experimental results show that the measured radiation pattern is much more flattened out than predicted and the observed oscillations cannot generally be imputed to the superposition of the SR emissions from the wigglers. For further reading: M. Silari and L. Ulrici, The effect of the polarization wigglers on radiation levels in the LEP tunnel, TIS-RP/IR/97-30.

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