Helmut Schonbacher

The Large Hadron Collider (LHC) in the LEP tunnel

After the remarkable start-up of LEP, the installation of a Large Hadron Collider, LHC, in the LEP tunnel will open a new era for the High Energy Physics. This report summarizes the main LHC parameters and subsytems and describes the more recent studies and developments.

Comparison of high-dose dosimetry systems for radiation damage studies in collider detectors and accelerators

Abstract Measurements of absorbed dose in accelerator tunnels around primary beam areas are carried out on a routine basis at CERN. Dosimetric surveillance of high-energy particle accelerators has a great importance for the assessment of the radiation induced damage to materials and components used in high-level radiation areas. Standard dosimeters used at CERN for this purpose are polymer-alanine dosimeters (PAD) and radiophotoluminescent glass dosimeters (RPL). Ethanol-chlorobenzene dosimeters (ECB) for high-dose dosimetry, developed at the Ruder Boskovic Institute (RBI), have several interesting properties making their use in future multi-TeV colliders and detectors promising. These and RPL dosimeters were compared using the CERN alanine dosimetry as the reference system and 60 Co gamma rays as the reference radiation. A very good agreement between the ECB and PAD was obtained for 60 Co gamma irradiation whereas RPL overestimated the dose by about 15%. In mixed accelerator radiation fields the combination of the three dosimeters opens the possibility to estimate the total dose and the quality of the principal radiations contributing to the total radiation field.

Effects of nuclear radiation on the optical properties of cerium-doped glass

Abstract Some twenty types of glass containing 0.5-4% CeO 2 have been irradiated in a 60 Co gamma cell and in the mixed neutron-gamma field of a nuclear reactor, at total integrated doses of up to 5 × 10 9 Rad (CH). The resulting colouration has been assessed quantitatively by measuring the light transmission with reference to air, in the range 360–510 nm. From the results, certain types of glass suitable for applications in nuclear engineering can be selected. Specifically, it was found that 1–2% CeO 2 content is usually sufficient to obtain radiation-resistant optical glass: the reduction in light transmission above 450 nm is nil at 10 8 Rad (CH), below 10% at 10 9 Rad (CH), and below 20% at 5 × 10 9 Rad (CH); the post-irradiation fading is negligible.

Effects of radiation types and dose rates on selected cable-insulating materials

Abstract A series of radiation tests have been carried out on halogen-free cable-insulating and cable-sheathing materials comprising commercial LDPE, EPR, EVA and SIR compounds. samples were irradiated at five different radiation sources, e.g. a nuclear reactor, fuel elements, a 60Co source, and in the stray radiation field of high-energy proton and electron accelerators at CERN and DESY. The integrated doses were within 50–5000 kGy and the dose rates within 10 mGy/s–70 Gy/s. Tensile tests and gel-fraction measurements were carried out. The results confirm that LDPEs are very sensitive to long-term ageing effects, and that important errors exceeding an order of magnitude can be made when assessing radiation damage by accelerated tests. On the other hand, well-stabilized LDPEs and the cross-linked rubber compounds do not show large dose-rate effects for the values given above. Furthermore, the interpretation of the elongation-at-break data and their relation to gel-fraction measurements show that radiation damage is related to the total absorbed dose irrespective of the different radiation types used in this experiment.

Radiation damage to electronic components

Abstract Characteristic properties are presented of some 40 different electronic components (resistors, capacitors, diodes, transistors, and integrated circuits) which were irradiated in a nuclear reactor up to 10 15 n/cm 2 ( E >1 MeV). Complete circuits (e.g. rf amplifiers and detectors, mixers, differential amplifiers, voltage-to-frequency converters, oscillators, power supplies) were irradiated near the CERN Intersecting Storage Rings up to 10 6 Rad (RPL) (dose measured with radiophotoluminescent dosimeters) under simulated operational conditions. Representative measured parameters, such as resistance, capacitance, forward voltage, reverse current, toggle frequencies, are given in graphs as a function of radiation dose. The results are discussed in detail and lead to the over-all conclusion that the operation of electronic components and circuits is seriously affected by radiation environments with doses in the order of 10 13 n/cm 2 or 10 4 Rad (RPL); some components and circuits fail completely at doses of 10 14 n/cm 2 or 10 5 Rad (RPL).

Degradation of acrylic scintillator and wavelength-shifter material by nuclear radiation

Abstract The effect of nuclear radiation on the spectral transmission, self-attenuation, and light yield has been measured for various commercially available acrylic scintillator and wavelength-shifter materials. The results are given in the form of graphs and show that at integrated doses below 10 3 Gy the change of spectral transmission is negligible, whilst at 10 4 −e10 5 Gy the transmission changes by 10–20% depending on wavelength.

A comparison of the radiation damage of electronic components irradiated in different radiation fields

Abstract Resistors, capacitors, silicon diodes and transistors, TTL integrated circuits, and operational amplifiers have been irradiated in three different radiation environments: in a research reactor with up to 1015 n/cm2 (E>1 MeV), near a proton beam of the CERN Intersecting Storage Rings with up to 5 × 105 Rad, and with a 30 kCi 60Co gamma source with up to 1 × 107 Rad. Representative parameters, such as resistance, capacitance, forward voltage, reverse current, toggle frequencies, have been measured before and after irradiation. It was found that, in comparison with nuclear-reactor irradiations, the effect of 60Co gamma rays can be smaller by a factor of 100 or more, whereas high-dose-rate accelerator irradiation can be up to 5 times more damaging for the same nominal amount of irradiation. It is concluded that care has to be exercised when interpreting the results of radiation damage tests on electronic components in different radiation environments.

Irradiation of Quench Protection Diodes at Cryogenic Temperatures in a Nuclear Research Reactor

Within the framework of the Large Hadron Collider (LHC) R&D programme, CERN and the Department of Physics E21 of the Technical University Munich have established a collaboration to carry out irradiation experiments at liquid helium and liquid nitrogen temperatures on epitaxial diodes for the superconducting magnet protection.

Effects of neutron radiation on the electrical resistivity of copper at room temperature

Abstract Industrial, oxygen-free, high conductivity (OFHC) copper and electrolytic tough-pitch (ETP) copper have been irradiated to a total integrated neutron dose of about 5 × 10 19 n/cm 2 ( E >0.1 MeV) at 40°C. Resistance measurements have been made at 22°C before and after irradiation. The radiation-induced increase in the electrical resistivity at a dose of 1.5 × 10 19 n/cm was ∼ 5% for annealed OFHC and ∼3.5% for annealed ETP coppers, respectively.

Evaluation of the radiation resistance of electrical insulation materials

Abstract The qualification of insulating materials for electrical cables is often accomplished according to the IEC 60544 standard of the International Electrotechnical Commission. The mechanical properties of the polymeric insulators are tested prior and after irradiation at relatively high dose rates. To assess the ageing of selected materials under realistic service conditions, usually at lower dose rate, an IEC Working Group has proposed extrapolation methods (IEC 61244-2), one of which is applied here for a cable sheathing material from Huber+Suhner. The method is found to be suitable to compare radiation resistance data of different materials irradiated under different conditions.