Radiation studies for the MI collimation system and ILC vertical cryostat test area December 13, 2006 Igor Rakhno Accelerator Physics Department

2 LARP Main Injector collimation system Vertical RF cavity test IB1

3 MI collimation system at slipstacking injection All that starts at MI230 location – 2 dipoles and 9 quads, 1 primary horizontal collimator and 4 secondary vertical ones. The region is about 120 m in length. Scraping rate for the primary collimator is assumed to be 5% of total intensity which is 5.5×10 13 ppp at 2.2 sec rep. rate. So we have (5.5×10 13 / 2.2) × 0.05 = 1.25×10 12 p/s lost. Primary collimator is a tungsten bar 0.2 mm in thickness. Issues addressed: groundwater activation, absorbed dose in the magnet coils, residual activation. E-cool equipment.

4 MI collimation system at slipstacking injection Dipole cross section

5 MI collimation system at slipstacking injection Primary collimator

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7 Usually epoxy can survive for absorbed dose up to 400 Mrad = 4 MGy. Our data is 0.1 MGy/yr (front of 1 st dipole) and 0.02 MGy/yr (front of 2 nd dipole). Lifetime of the 1 st dipole ≈ 40 years.

8 MI collimation system at slipstacking injection Secondary collimators

9 Vertical RF cavity test IB1 Three vertical test cryostat facilities for SRF cavities are planned to be installed in IB1 in TD. A single cavity test lasts no less than 18 hours and about 400 cavities are planned to be tested a year. The first facility should be available in The operations will be focused on high accelerating gradients– from 20 up to 50 MV/m. The facility can be a strong radiation source (including neutrons). Contacts and comparisons – JLab and DESY. Major drawback – there is no reliable model describing the amount, spatial, energy, and angular distributions of the field-emitted electrons inside the SRF cavities. Surface imperfections and residual gas contamination. Dark current ≈ 2 µA.

10 Vertical RF cavity test IB1

11 Vertical RF cavity test IB1 Two models were introduced – an electron beam hits the inner wall of the cavity. A conservative approach. Dose attenuation has been calculated. The results of the calculations are normalized using the existing experimental data on measured dose rate in the vicinity of such SRF cavities – the data from DESY. A tradeoff is sought – from operational standpoint people prefer bigger external shielding and stronger motors than small local shielding with lower efficiency of cryogenic operations, reduced level of detector signal inside, and duplication of the local shielding blocks several times. The area will qualify as a controlled area (prompt dose rate under 5 mrem/hr).