Wednesday April 15, 2015

We will meet in TL 2221 on Wednesday April 15 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- Bubble Chamber progress at Argonne

media:bubble_photo_April2015_1.jpg

media:bubble_photo_April2015_2.jpg

media:Hg_N2O_1.gif

media:Hg_N2O_2.gif

media:Hg_N2O_3.gif

media:Hg_N2O_4.gif

media:Hg_N2O_5.gif

media:Hg_N2O_6.gif

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Notes from this meeting:

• Bubble Chamber:

1. The bubble chamber is operational. The above movies show a 50 ms (5 frames) of bubble formation and quenching.
2. The operational temperature is -10°C and at 20 atm. To quench the bubble, the pressure is raised to 50 atm.
3. Initial background and neutron source tests indicate that the chamber is working as expected. The cosmic background rate is about 1 bubble every two minutes.
4. The only remaining issue is the mercury droplets at the inner wall of the glass cell. These droplets got stuck there when the chamber was being filled with N₂O. Mercury is not supposed to behave this way but it did.
5. Since mercury has a low threshold for (γ,n) reactions: 6.2 MeV for ²⁰¹Hg (NA=13%) and 6.7 MeV for ¹⁹⁹Hg (NA=17%), we must get rid of this possible source of background.
6. Two ideas to get rid of mercury:
   1. New coating of dry film on inner wall of the glass cell
   2. Use ultrasonic shaker to force the droplets to the bottom of glass cell
7. Bubble Chamber stand needed for installation at JLab will be built at Argonne.

• Schedule:

1. The pressurized vessel safety review will be done by May 15^th
2. The chamber will arrive at JLab by June 15^th
3. Installation in JLab Injector will be in the first two weeks of July
4. Commissioning with no beam is planned in the second half of July
5. Two weeks of engineering run in August and September (two shifts per day)

• Engineering Run:

1. The chamber will be filled with natural N₂O (i.e., no enriched ¹⁶O)
2. Beam energy: 6 - 9 MeV
3. Beam current: 0 - 100 µA