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

Notes from this meeting:

The bubble chamber is operational. The above movies show a 50 ms (5 frames) of bubble formation and quenching.
The operational temperature is -10°C and at 20 atm. To quench the bubble, the pressure is raised to 50 atm.
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.
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.
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.
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
Bubble Chamber stand needed for installation at JLab will be built at Argonne.