Parity Mtg, 18 May 2007 Bob Michaels Lead Target and Warm Septum Interface Performance of Lead Target during e06007 Radiation for PREX, extrapolated from e06007 Short update on Septum Interface.

Parity Mtg, 18 May 2007 Bob Michaels E06007 Lead Target Performance E06007 Pb(e,ep) ran Mar 5-20, 2007 Pb/diamond target like PREX Pb 0.17 mm (PREX 0.5 mm) diamond 0.15 mm (same PREX) 2 55 uA no failure Ramped to 85 uA target melted ! Ran 2 nd 45 uA 2 weeks no failure Calibrate simulations of radiation

Parity Mtg, 18 May 2007 Bob Michaels Pb #4 Ran 2 45 uA Pb #3 Ran 2 55 uA Failed near 85 uA E06007 Lead Targets discoloration from beam (rastered)

Parity Mtg, 18 May 2007 Bob Michaels Monolithic Target Multilayer Target Q Heat Load t t (thickness) Conduction t Temp. Indpt. of t C / Pb / C Pb is an extra heat load for C. Target Heating Considerations Model assumes good contact !

Parity Mtg, 18 May 2007 Bob Michaels diamond lead PREX heat loads E06007 lead is 1/3 this Temp at center ~ ½ PREX (not quite 1/3 ) Did not expect e06007 melting But if no contact, lead ~ 40 uA. (3x3 raster) Extrapolate to PREX (assumes same contact) Temperature : Extrapolating from E06007 Safe: 27 uA Melt : 40 uA Guess: temp at border ~ 50 K (indpt. of thickness)

Parity Mtg, 18 May 2007 Bob Michaels Target Heating -- Conclusions Want good thermal contact. Will vacuum grease help ? Need procedure to center target. Need more test beam ? Pure hydrocarbon, high conductivity, low vapor pressure e.g. Apiezon L

Parity Mtg, 18 May 2007 Bob Michaels Lead Radiation Lead E06007 Pb(e,ep) Mar 5 – 20, 2007 Hours in plot Calibrate simulation Extrap. to PREX Report by Bob M. & Pavel Degtiarenko: prex_rad.pdfhttp://hallaweb.jlab.org/parity/prex/

Parity Mtg, 18 May 2007 Bob Michaels Site boundary neutrons (photons add ~25% more) Lead e06007 Bad beam tune

Parity Mtg, 18 May 2007 Bob Michaels E06007 PREX Lead Diamond 105 Beam Energy (GeV) Beam Current Calc. Rad. Rate Measured Rad. Rate Accumulated Radiation (calculated) 0.5 mrem 2.2 mrem (22% budget) Accum. Radiation (measured) < 0.30 mrem --- Factor of ~2

Parity Mtg, 18 May 2007 Bob Michaels Radiation -- conclusions PREX: 22% yearly site boundary budget Probably ~1/2 that (estimates are conservative) Factor of 4 – 10 more radiation inside hall A. But dont use the bad beam tune experience as a guide. May need local shielding on IOCs on downstream beamline. ( For PREX compared to e06007 ) ( last 5 days e06007 had beam scraping )

Parity Mtg, 18 May 2007 Bob Michaels