CHIPS Run May-2008
Goals
- Determine smallest beam spot size using JLAB flags at the zero degre port and after the 90 degree bend on the 25 MeV machine current beam line
- Install FC and measure its performance (smallest controllable current attainable)
- Measure background rates for positron production
Run Plan
May 27,2008
Spend Day tuning with the following goals
1.) Minimize beam spot size on zero port and document with image grabber. 1 mm diameter beam spot size is the goal.
2.) Check spot size on flag after 90 degree bend. Tungsten target out
3.) Try to retune the beam spot after the 90 degree bend to a 1mm diameter
4.) Optimize transmission to FC.
5.) loop over 1-4 to find tune which delivers highest transmission and smallest beam spot size.
May 28, 2008
1.) turn on NaI and HpGe detectors.
2.) minimize background
3.) show the gamma is from positrons buy doing Tantalum target in -vs- out measurements, inserting the last phosphorous flag to stop the positrons, and changing the last 45 degree dipole magnet . The last dipole will remove the positron source and transport most of the photons.
May 29, 2008
Measure 0.511 keV gammas as a function of beam current
May 30, 2008
Solvable Problems:
1.) JLAB would like beam spot of 1 mm. Measured 8 mm after thick window. Doug reported measuring 3 mm without thick window.
2.) Lowering beam current: 10^8 electrons/pulse desired to produce 1 positron per pulse. Perhaps slits can solve the above problems and then localized lead shielding to reduce backgrounds.
3.) Beam position monitoring. Flags from JLab have arrived Brett will look into installing.
May run on IAC schedule for 27,28,29,30 need cameras for the flags.
Next steps after Feb run:
1.) Optimize develop beam line design. Serkan needs more input about the IAC beam properties.
2.)Proposal is to measure beam properties with flags and FCUP during May 27-30 run. (parts to install beam line flags is critical path defining the run start date).
a.)Measure beam shape at zero degree port and after 90 degree bend
b.) install FCUP (2 3/4 flange)
c.) measure background rates
i.) one flag has positron converter in experimental cell.
ii.) dipole on experimental cell side
iii.) photon veto using scintillators
3.) Future beam line
a.) perhaps move converter target between dipole b.) 50 ns beam pulse may give you +/- 2 MeV spread
Targets
1.) Tantalum foil 2.0 mm (99.5% metals basis) lot # D11S010, stock # 10357
2.) Tungsten foil, 1.0 mm thick, 99.5% metals basis, LOT # H23R015, stock #13981
Phosphorus targets:
3.5 cm center to center distance between mount bolts.