Low energy particles which are impacting on the inner wall of the vacuum chamber will deposit their energy in the cold part of the cavities which may lead to a loss of superconductivity. The energy of particles passing the first acceleration cavities is too low that their particle shower in case of an impact on the equipment could be detected outside of the acceleration structures. Therefore sensors need to be placed inside the cold on the outside of the vacuum chamber. Also these detectors need to be optimized for the protection of equipment and the optimisation of the beam parameters.

In case of LHC it is expected that the limit for instantaneous luminosity will be determined by beam losses on SC magnets in the experimental insertion regions. To allow an optimal detection of the energy deposition in these magnets, the detectors need to be placed close to the protected elements which are SC coils. This implies installation of the particle detectors in the cold mass of the magnets. Dose measuring devices operating at 2 Kelvin have neither been used nor described in the current literature, but will be studied and developed in the frame of this project in partnership with CIVIDEC, the RD42 collaboration at CERN and the St. Petersburg Ioffe Physical-Technical Institute of Russian Academy of Sciences. The selected detectors for cryogenic irradiation test are a silicon (Si) and single crystalline chemical vapour deposition diamond (scCVD). In a theoretical part of the project the irradiation impact on silicon and scCVD diamond detectors will be simulated. To allow a deep understanding of cryogenic BLM materials the laser transient current measurement technique (TCT) at cryogenic temperatures on silicon and scCVD diamond detectors is foreseen to be done. The ultimate goal of the project is the preparation of cryogenic BLM prototypes to be placed inside the cold mass of a LHC SC magnet in 2018, when the machine will be stopped again for upgrade.

Initial studies have been done in the context of two PhD theses one focusing on scCVD detectors using an alpha particle source for tests down to 2 Kelvin and by the other focusing on the irradiation of Si and scCVD detectors and studying the magnitude of sensitivity decrease with increasing fluence.

The final goal of the project is an exhaustive characterisation of the Si and CVD detector materials at 2 Kelvin and in high radiation fields. The investigation by the trainee should allow a well based decision on the placement of such a detector in the cold mass of a SC magnet where no access for maintenance is possible.

The beam loss detection at low particle energies is also a concern for high intensity linacs with SC cavities, like International Fusion Materials Irradiation Facility (IFMIF).

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