Maximum Credible Beam Loss in the Main Injector D. Capista January 26, 2012

2011 Operation Data Protons delivered to:  Antiproton source: 5.75e19  NUMI: 2.72e20  Switchyard: 7.26e16  Recycler: 8.54e13  Tevatron: 4.30e15  MI Abort: 2.49e18 Total injected beam = 3.50e20 Total beam delivered to it's destination = 3.32e20 Beam lost in MI enclosure = 1.79e19 protons Lost beam intercepted by the collimator system = 1.70e19 – Collimators are 95.1% efficient at capturing lost protons based on loss monitor readings 8.97e17 protons were unaccounted for in the MI tunnel in the past year,.25% of the total beam.

Accident Analysis  Determine the most likely value of dNbeam/dt and its upper limit for each scenario. The upper limit compared with the most likely value may be useful to determine the uncertainty in the analysis.  Determine the most likely values of Δt beam and its upper limit for each scenario. The upper limit compared with the most likely value may be useful to determine the uncertainty in the analysis.  In all scenarios, any beam loss over 10% of full intensity (5E13), will most likely trip the machine in a single pulse.  A single point loss will trip with much less than 10% loss  There exists a case, in all scenarios, where due to equipment and administrative failures, the entire beam can be lost repeatedly for extended periods of time.

Machine protection systems Beam Switch Sum Box (BSSB) – A logical collection of the individual machine permits combined with beam switches and operator programmed timing that produces a beam request at the Preaccelerator pulse shifter Example; Beam to the NuMi target requires: – permits from Linac, Booster, MI8, Main Injector, and Numi – NuMi beam switch – Proper clock events from the Time Line Generator (TLG) » Clock events must be in the proper sequence – BSSB can be single point failure but the proper TLG events need to be in place

Machine protection systems Main Injector permit system (abort system, CAMAC 200) – Accepts digital inputs from devices to determine whether a permit is allowed or denied. – Generates a beam abort when the permit drops – Requires operator reset after the permit drops – Devices that are connected to the permit system include: Beam Loss monitors Power supplies Vacuum valves RF systems Safety system MI control system software monitoring Miscellaneous inputs (service building doors)

Beam loss scenarios Correction elements with straight beam pipe 8 Gev projection with a 20A setting (limit) of a correction element  Beam is lost over about a meter with a 20π beam and 3σ area Diagram From Ming-Jen yang

Beam loss scenarios Correction elements with straight beam pipe 120 Gev projection with a 20A setting (limit) of a correction element  Beam can not hit the beampipe Diagram From Ming-Jen yang

Beam loss scenarios Example of a kicker loss profile at MI10 MI-10 Max. 100 mr/hr Data from This profile resulted from the injection kicker firing through Circulating uncaptured beam. This loss has been mitigated by the gap clearing Kicker. Diagram from Peter Kasper

Where can we have a near single point loss? Tight aperture restrictions  Collimators Difficult if not impossible to hit directly at high energy as correction elements will have to sweep the beam. MI8 line at 836 and 838 – Restricted to 8 Gev MI30 area at 301, 303, 307, and 308 – Used below 20 Gev in normal operation  Lambertsons MI Located at 101, 222, 321,402, 522, 608, and 620 – For NoVA 222,321,and 630 are removed. 306 is installed  Lambertsons RR (limited to 8Gev) Located at 214, 328 and 402 – For NoVA 214 and 328 are removed. 232 is installed

Lambertson Losses Projection of an extraction area Consisting of three lambertsons And a quadrupole magnet. Lost beam will usually hit the strike zone Beam can be lost with either a correction element or a kicker Beam lost due to a correction element will be lost over many turns if the loss occurs above 8Gev Beam lost due to a kicker will be single turn

Lambertson Losses Example of a Lambertson loss pattern from a small chronic loss Activation is primarily on the first Lambertson, but is also distributed over 50 feet. MI-40 Max. 69 mr/hr Diagram from Peter Kasper

Further Thoughts Hitting a Lambertson with a KW beam will heat it up and most likely cause vacuum activity and close the vacuum valves. Beams-doc-36-v1 “Burning up the Beampipe” concludes that “the beampipe will never melt as a consequence of the beam striking it at some small incident angle”. Beams Document 741 “Main Injector Shielding Verification” points out that losses in LCW cooled components activates the water. “Monitoring of other high beam power future projects such as Miniboone and NUMI should take precautions to ensure LCW systems which exist in areas accessible by personnel are monitored and protected if necessary. In addition, if water cooled components are used in beam transport lines, monitoring dose rates from LCW return headers might be useful in providing compensation for marginal shielding design”.