Wednesday August 7, 2013

We will meet in TED 2561B on Wednesday August 7 at 3:00 pm EST.

For those calling in we'll use the ReadyTalk audio conference system.

1. Dial Toll-Free Number: 866-740-1260 (U.S. & Canada)
2. Enter 7-digit access code 4402297, followed by “#”

Agenda:

 media:Meeting_7August_2013.pdf
 media:Meeting_7August_2013.pptx  

1- Bubble Chamber progress at Argonne

2- Beam Heating in Cu Radiator media:Beam_Heating_in_Cu_Radiator.pptx media:Beam_Heating_in_Cu_Radiator.pdf

3- Beamline Layout

4- Bubble Chamber cost estimate: procurement and labor

5- Background from ¹⁷O(γ,n)¹⁶O and subsequent neutron elastic scattering with ¹⁶O and ¹⁴N nuclei

6- Background from ¹³C(γ,n)¹²C (in case we decide to use CO₂ instead of N₂O)

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Notes from this meeting:

• Bubble Chamber:

- In the process of changing the buffer liquid from water to mercury (volume = 0.5 l)
- Electron beam with full power directly hitting the chamber for few ms will do no harm

• Radiator:

- Heating of the radiator seems not to be a problem. Dave will do more heating calculations with a real model
of the radiator ladder

• Beamline Layout:

- Need a Faraday Cup on the Bubble Chamber beamline, after the second BPM and before the radiator
- On the main beamline, FC2 is a 1 kW dump (200 µA and 5 MeV)
- PEPPo took positron data with Quads OFF and electron data with Quads ON
- The Bubble Chamber experiment needs electron beam with KINETIC ENERGY = 8.5 MeV
- At Jefferson Lab, an egress has a minimum clearance of 36 inches
- We can use two Super Harps instead of the two Quads. Unfortunately, the accelerator does not have Super Harps, 
and it costs $10,000 each. 
- Electron Dump: isolated to measure beam current, 2 kW dump. Make sure no neutrons are produced in the ceramic insulator
- Plan to have both BCM0L02 and Electron Dump in Beam Loss Accounting (BLA)
- The photon Cu collimator has a hole of about 1.0 cm diameter
- The only Fast Valve in the Injector is located just downstream of the Injector Gate (VFV0L04).
- Fast Valve closes in 30 ms and comes with its own vacuum gauge that can be installed separately on the beamline.
The trip level is adjustable - typically around 5x10-7 Torr.
- The Fast Valve and its electronics cost $18,000 (valve=$7k and controller=$11k) 

• Cost:

- Include procurement and labor overhead

• Beam Energy:

- What is our requirement on the relative beam energy uncertainty. This uncertainty is about 0.1% and is dominated 
by the magnet power supply uncertainty of few mA.
- During PEPPo, achieved 8.25 MeV/c, or 7.75 MeV kinetic energy. The Bubble chamber needs 8.5 MeV kinetic energy.
  As part of commissioning, we need to process the 1/4 cryo unit to be able to achieve 8.5 MeV kinetic energy  

• Simulations and Backgrounds:

- Discriminate between (γ,α) and (γ,n) events using the acoustic signal. The acoustic signal may help to
reduce (γ,n) by a factor of 10 to 100
- Planning to measure the exact depletion of 17O and 18O. Now, it is an upper limit of <10-6
- For CO2, we need also to worry about 12C(γ,3α) background reaction
- Full GEANT4 model of the experiment. What is the photon flux? What is the size of the photon collimator? 
What is the sensitivity to misalignment? What is the allowed beam size on radiator? ...
- Full FLUKA model of the experiment. What is the photon flux? Calculate neutron background
- It is a good idea to put a photon detector in place of the photon dump to measure the Bremsstralung flux and
check for misalignment