Bubble Chamber Meeting Wednesday December 9, 2015

We will meet in TL 2221 on Wednesday December 9 at 3:30 pm EST.

For those calling in we'll use the Blue Jeans [1] audio conference system.

Phone number: 1-888-240-2560
Meeting ID: 3528502673#
Meeting URL: http://bluejeans.com/3528502673

Agenda:

1- Experiment Schedule (listed as Injector Facility Development Time): [2]

2- Bubble Chamber work at ANL

3- Sept beam test data analysis: media:Rate_N2O.pdf media:Rate_N2O.pptx

4- Discussion of June 2016 beam test: media:sigma_f19ga_low.pdf

5- Summary of Sept Beam Test: media:BeamTest_Summary_II_Sept2015.pdf media:BeamTest_Summary_II_Sept2015.pptx

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Notes from this meeting:

• Schedule in 2016:

1. Beam Test Run II: May 30 – June 20
2. Beam Test Run III: Aug 15 – Aug 29
3. Installation of chamber in Injector can be in:
   1. April 14 – April 30, 2016 (while accelerator scheduled for Cryo Configuration Change), or
   2. During first week of Run II.
4. Modification to beamline can be during:
   1. Winter Shutdown (Jan 4 – Jan 27, 2016), or
   2. April 14 – April 30, 2016.

• Brad is preparing to change chamber to single fluid with new cooling system.

1. Do we want to change to a collimator inside chamber? made of silver instead of copper?
2. Do we want to use hydraulic oil with higher hydrogen content to help moderate fast neutrons?

• Recent data analysis results:

1. Cosmic rate in chamber fiducial volume at JLab Injector is about 10^-3 Hz (or 1 event every 15 minutes) – one order of magnitude smaller than HIGS or Argonne (due to 15 ft of soil and water shielding at injector).
2. Large deadtime correction has to be applied since we ran at very high rate. We should have used lower beam current than 40 nA. Unfortunately, we did not plan then for very low beam current. We could have used Hall B laser instead of Hall A where we could deliver about 1 nA reliably. To run at very low current, we need to re-install the ceramic break to be able to measure beam current with a picoammeter; BCM is only good for currents above 5 nAs.
3. For ¹⁷O(γ,n)¹⁶O calculated rate, one must account for chamber threshold of about 100 keV energy of recoil ¹⁶O ion.

• Plan to use C₂F₆ in Beam Test Run II to measure ¹⁹F(γ,α)¹⁵N:

1. Only one isotope: ¹⁹F
2. Electron beam kinetic energies: 4.0 – 5.5 MeV (below threshold for neutron or proton reactions); may require new radiator and collimator.