parity mtg, 18 may 2007 bob michaels lead target and warm septum interface performance of lead...
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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,e’p) 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 days @ 55 uA no failure
• Ramped to 85 uA target melted !
• Ran 2nd target @ 45 uA 2 weeks no failure
• Calibrate simulations of radiation
Parity Mtg, 18 May 2007 Bob Michaels
Pb #4Ran 2 weeks @ 45 uA
Pb #3Ran 2 days @ 55 uAFailed near 85 uA
E06007 Lead Targets
discoloration from beam (rastered)
Parity Mtg, 18 May 2007 Bob Michaels
Monolithic TargetMultilayer Target
Q
Heat Load t
t(thickness)
Conduction tTemp. 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
2/73 cmW2/376 cmW
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 melts @ ~ 40 uA. (3x3 raster)
Extrapolate to PREX (assumes same contact)
Temperature : Extrapolating from E06007
Safe: 27 uA Melt : 40 uAGuess: 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,e’p)
Mar 5 – 20, 2007
Hours 1450 - 2010 in plot
Calibrate simulation Extrap. to PREX
Report by Bob M. & Pavel Degtiarenko:
http://hallaweb.jlab.org/parity/prex/prex_rad.pdf
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 193 568
Diamond 105 105
Beam Energy (GeV) 2.65 0.85
Beam Current 42 50
Calc. Rad. Rate. 0.7 3.1
Measured Rad. Rate. 0.35 ---Accumulated
Radiation (calculated) 0.5 mrem 2.2 mrem
(22% budget)
Accum. Radiation (measured) < 0.30 mrem ---
2cm
mg
2cm
mg
A
hrrem /
hrrem /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 don’t 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