Answers/considerations to the questions raised on the last ASSRC meeting on Sept. 24, 2013

The following is my summary from emails, private communication and some simulation & calculations (about moving roman pots to between DX & D0)

Items arranged as in the order of the minutes …

Dec. 6, 2013

Kin Yip / Liaison PhysicistES & F

Consider accident scenarios at the DX location due to DX magnet movement, inadvertent optics changes, or other machine anomalies that may steer beam onto the Roman Pot windows

Probably impossible to prove what’s impossible … A max. of ~ 10 bunches may hit the window (probably in multiple turns) in the weirdest scenario (but the calculation below doesn’t depend on this no.)

Perform beam particle analysis for full beam intensity, and luminosity. Calculate stress yield due to temperature rise on window at full beam intensity and beam spot size.

Since the beam size at DX is significantly larger than in the past (between Q3 and Q4), the (peak) energy deposition on the roman pot window is much lower than before (by >an order or two of magnitudes) No problem for the thermal/mechanical stress even we assume all possible proton beam (2.51013 protons) dumped on a single spot of the window in one instant (See C. Pai’s report).

Review NMC vs BLM operation or the use of both. Investigate electronic noise issues with NMCs to prevent inadvertent beam aborts. (Due prior to Run 15).

D. Gassner has agreed to connect the entire actual ground loop with the motor and the NMC in the coming run (without beam permit of course) and monitor/observe any noise during the coming run (2014). The experimental group probably has the greatest interest not to have this kind of noise. BLM has been considered more than once before but it doesn’t seem to be as fast as NMC.

Estimate the time to remove beam from the machine when a NMC trips to determine if the time delay is adequate for machine protection.  

J. W. Glenn has given some detailed consideration and written (eg.) in the ASSRC Note of 2003-4-11. We’ve been using this NMC system for a few times/years since then and it’s proven to be sensitive/robust.

Estimate operational down time and effect to RHIC vacuum, if a vacuum loss occurs in the Roman Pot.

M. Mapes: The downtime could be one week which includes a chamber repair and some time for a bake. Determine effect upon Be beam pipe in STAR with a catastrophic vacuum loss in the Roman Pot.

M. Mapes: The Be pipe would have no impact from a catastrophic leak since the pressure would essentially be equaled to one atmosphere.

Review/ update Operation Procedure OPM (TPL 09-09) for PP2PP operations. (P. Ingrassia, due prior to Run 15).

Will be done in due course

NMC response time ~ 6 ms (Woody’s “Background” in ASSRC Note of 2003-4-11).

Beam size used in simulation:2009 : x = 0.056 cm; y = 0.043 cm; Now : x = y = 0.28 cm (assuming 15 in emittance ) at 100 GeV

x = y = 0.181 cm (assuming 15 in emittance ) at 255 GeV