ColMat - Collimators & materials

for higher beam power beam

(Work package 8)

Objectives:

Allowing the exploration of unknown territories in basic research with proton and ion beams. As a consequence, new challenges arise for the materials that are placed close to or into the high intensity beams, mainly but not exclusively inside collimators. Full intensity and performance can only be reached if collimation works reliably (minimum downtime) with excellent efficiency. Damage must be avoided or, if it cannot fully be excluded, handled in a safe manner (selfrepairing devices).

This work package addresses R&D on materials and collimators for high intensity beams. The following objectives have been defined:

• Coordination and scheduling of the WP tasks
• Monitoring the work, informing the project management and participants within the JRA
• WP budget follow-up
• Design collimation systems for high-intensity proton and ion beams, adequate for achieving the performance goals of LHC and FAIR.
• Predict energy deposition from different sources for LHC and FAIR.
• Identify and fully characterize in experiment and simulation materials that are adequate for usage in high power accelerators.
• Predict residual dose rates for irradiated materials and their life expectancy due to accumulated radiation damage.
• Design, construct and test a collimator prototype for upgraded LHC performance
• Design, construct and test one cryogenic collimator prototype.
• Develop crystal engineering solutions for collimation.

Description of work:

Task 1. ColMat Coordination and Communication. The activities of this task are to oversee and co-ordinate the work of all the other tasks of the work package concerned, to ensure the consistency of the WP work according to the project plan and to coordinate the WP technical and scientific tasks with the tasks carried out by the other work packages when it is relevant. The coordination duties also include the organization of WP internal steering meetings, the setting up of proper reviewing, reporting to the project management and the distribution of the information within the WP as well as to the other work packages running in parallel.

The task also covers the organization of and support to the annual meetings dedicated to the WP activity review and possible activity workshops or specialized working sessions, implying the attendance of invited participants from inside and outside the consortium.

Task 2. Modelling, Materials, Tests for Hadron Beams. The first challenge concerns safely intercepting and efficiently absorbing unavoidable losses from high intensity proton and ion beams. This includes protection of the accelerator against excessive energy deposition (leading to quenches of superconducting magnets and interruption of operation) and beam-induced damage, while maintaining an ultra-high vacuum. The study of innovative collimation systems is required, which place appropriate materials at optimized locations in the accelerator rings. This topic is addressed in sub-task 1. Connected to this is the energy deposition from particle losses and their associated particle cascades. This includes energy deposition in warm regions, in superconducting magnets and in experimental insertions (problem of background) for losses from different sources. This topic is addressed in sub-task 2. The third research theme is the study of appropriate materials for usage with high intensity beams. Issues include a review of suitable materials, characterization of standard and advanced materials, mechanical modelling of material behaviour and resistance to extreme thermal shock waves. This topic is addressed in sub-task 3. Finally, the fourth research topic treats the residual doses due to irradiation with lost particles (protons and ions) and the radiation-induced damage to materials. This topic is addressed in sub-task 4.

Sub-task 1: Halo studies and beam modelling.

1. Nature, magnitude and location of beam losses in modern accelerators.
2. Dynamics of the beam halo and proper diffusion models.
3. Design and optimization of multi-stage collimation systems.
4. Simulation of multi-turn collimation processes, including nuclear interactions of halo particles in the collimator materials.

The following institutes contribute to this work: CERN, GSI, CSIC, INFN, ULANC, UM and UNIMAN.

Sub-task 2: Energy deposition calculations and tests.

1. Showering models with protons and ions in the relevant energy range.
2. Modelling of the accelerator geometry and materials.
3. Energy deposition calculations for various operational assumptions.
4. Calculation of residual dose rates.
5. Modelling of radiation-induced displacements per atom (dpa).

The following institutes contribute to this work: CERN and GSI.

Sub-task 3. Materials and thermal shock waves.

1. Selection of candidate materials for usage in high intensity accelerators. This includes also special materials, like modern composite materials and crystals.
2. Mechanical, electrical and vacuum characterization of materials.
3. Simulations of thermal shock waves due to impacts of beam particles.
4. Experimental tests on material resistance to beam-induced thermal shock waves.
5. Modelling of beam shock-induced damage of accelerator materials.

The following institutes contribute to this work: AIT, CERN, GSI, EPFL, RRC KI, POLITO and RHP

Sub-task 4: Radiation damage.

1. Experimental tests on material resistance to beam-induced radiation.
2. Modelling of radiation damage for accelerator materials.
3. Prediction of material life expectancy in accelerator environment.

The following institutes contribute to this work: CERN, GSI and RRC KI.

Task 3. Collimator Prototyping & Testing for Hadron Beams The robustness, efficiency and vacuum quality of the collimator solutions specified in Task 2 must be established with prototypes and realistic particle beams before installation into a sensitive accelerator environment. This task supports the construction of prototype collimators for LHC and FAIR and the subsequent tests. Required resources are centred at the big accelerator laboratories, as these have the knowledge to build such devices. It is, however, mentioned that LHC upgrade collimators are also prototyped in collaborating institutes in the United States through the DOE funded collimation work package in the LARP program (total value of 5M$).

This task foresees the prototyping and testing of both room-temperature (LHC baseline type) and cryogenic (FAIR baseline type) collimators:

• One room temperature collimator will be designed for collimation close to the circulating beam. The design should improve the cleaning efficiency, reduce collimator-induced impedance, optimize radiation impact, improve operational handling and provide ultrahigh vacuum. Optionally it can include a bent crystal for exploitation of crystal-enhanced collimation, an advanced R&D topic in the accelerator field.
• A cryogenic collimator will be designed to avoid uncontrolled beam losses and therefore the production of desorption gases. A comparatively warm 0.6 m long wedge (50 K - 70 K) will be situated in a chamber cooled by liquefied helium at a temperature below 10 K. Therefore the wedge will desorb only a small amount of gas when hit by the beam, while the cold surfaces act as cryo pumping system.

The two types of collimators complement each other and can be used also in the other accelerator, for example LHC collimation could be improved with cryogenic collimators originating from a FAIR design. This illustrates the highly beneficial impacts of European collaboration.

Sub-task 1: Prototyping, laboratory tests and beam tests of room-temperature collimators (LHC type). The following institutes contribute to this work: CERN, INFN. Collaboration with BNL, FNAL and SLAC in the United States.

Sub-task 2: Prototyping of cryogenic collimators (FAIR type). The following institutes contribute to this work: GSI, CERN

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An illustration of the cryocatcher chamber within the SIS 100 Quadropole Cryostat. The SIS100 is one of the main accelerators at FAIR in GSI. Image courtesy of GSI.
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Cryocatcher test setup, planned for 2010: yellow=Test-beam, violet=cryocatcher, red= thermal copper shield, grey= cryostat. Image courtesy of GSI