From HallCWiki
Jump to: navigation, search

Hall C A1n/d2n Meeting Minutes

Collaboration Meetings

August 15, 2012

Attendees: T. Averett (W&M), Paul Brindza (JLab), G. Cates (UVa), J-P. Chen (JLab), Al. Gavalya (JLab), C. Keppel (JLab), P. Rossi (JLab), B. Sawatzky (JLab), P. Solvignon (JLab), S. Wood (JLab), Zhiwen Zhao (UVa), X. Zheng (UVa), Bogdan Wojtsekhowski (JLab), S. Wood (JLab); on the phone: Z-E. Meziani (Temple)

The meeting goal was for Thia and Patrizia to get up to speed on the polarized 3He target plans and R&D necessary. Agenda and slides can be found here.

The next meeting should be in about a month.

  • Thia gave her best estimate on when A1n in Hall A could be put on the floor:

- First beam in HallA scheduled for March 2014. This date shouldn't be affected by the re-baseline.

- FY16 is the most probable time to run A1n in Hall A

  • Steve gave on overview of the 12 GeV experimental schedule in Hall C:

- d2n and A1n could run during FY17 if re-baseline is not too severe. Not expected to be too bad for Hall C.

- For more details, see slides.

  • Jian-Ping gave an summary of the requirements for each experiment and an overview of the past pol. 3He running

- Patricia raised the issue of the density fluctuation along the 60cm-target chamber with 60uA beam. Gordon said that they certainly will check it but expect about 10% fluctuation at worse.

- A lot of discussions went on about the price tag that goes with each target luminosity improvement (see last slide).

- For more details, see slides.

  • Gordon presented several options for the target system.

- The design of a support box on which the oven and shielding plate are mounted at the top. This will require the reconfiguration of the existing Helmholtz coils.

- The barrel will be a great solution for the field uniformity issue but brings other concerns, as the difficulty to change cells.

- Gordon group has all the design done on the box and is ready to order it (without required financial help from JLab).

- With high field gradient, AFP will be used only for calibration not for polarization monitoring during the experiment: polarization loss would be too large.

- Water calibration will be difficult to perform with the target design considered at present. Jian-Ping insisted that two independent calibrations are very important. Gordon suggested to perform an extended study and calibrate EPR against water in the target lab.

- For more details, see slides

  • Todd gave an update of the new laser

- The laser died after about 1500 hours used.

- Todd is talking with the company to solve some issue with the laser.

- For more details, see slides

  • Al explained that the reconfiguration of the Helmholtz coils is not cheap. For each design step of the target system he is keeping in mind that it will have to fit on Hall C pivot too. The vertical dimensions have more constraint in Hall A and the horizontal dimensions have more constrains in Hall C.

  • Patricia explained that the fifteen 120m long optical fibers needed will be one of the major cost of the installation. She is waiting for the quote. Using a small version of the Qweak "Doghouse" for the laser might be much cheaper: damaged fibers can easily be replaced but laser safety system will have to be put in place.

- For more details, see slides

  • Zhiwen gave an overview of activities in the EEL target lab. The main point is that full tests cannot be done due the lack of good lasers and electronics.

- For more details, see slides

January 5, 2012

Attendees: T. Averett (W&M), G. Cates (UVa), J-P. Chen (JLab), D. Gaskell (JLab), B. Hesman (UNH), W. Korsch (UK), Z-E. Meziani (Temple), B. Sawatzky (JLab), P. Solvignon (JLab), S. Wood (JLab), X. Zheng (UVa)

The meeting goal was to gather all the spokespeople of the Hall C A1n and d2n experiments for discussion on the polarized 3He target plans. The general consensus was to use the same target system in Hall A and Hall C. Commissioning of the target system (A1n) would be likely in Hall A in 2015. In Hall C, the very preliminary schedule would put the start of A1n and d2n at the end of 2016.

Everybody agreed to meet every 3-4 months.

  • Beam polarimetry:

- Dave said there won't be any problem to get a 2% systematics from the beam polarimetry but to get 1% he will need users contribution.

- However it doesn't seem that the two experiments need that level of precision after looking at the other systematics.

  • Coils:

- The important aspect is that the holding field should be uniform in the pumping chamber. With convection, the polarized gas in circulating so fast in the target chamber that a minimal holding field to limit the depolarization should be enough.

- Zein-Eddine suggested two small solenoids, one for the pumping chamber and one for the target chamber. Multiple advantages can be seen if it would work: smaller system which will fit easily on the Hall A and Hall C platform, more room to access the target during the experiment and therefore work can be done safer and faster (ALARA). The coil design would have to work for longitudinal and transverse running.

- Concerns on the Hall C iron platform were expressed.

- Need an estimate of the fringe field from the SHMS. Paul Brindza said in the past to Brad that it won't be a problem. It will be nice to have numbers/field map to integrate in the coil design optimization.

- The UVa group is working on the holding field/coil design and will test the different ideas suggested during the meeting.

  • Target:

- Todd reminded that it was seen in the past that too much laser power on the pumping chamber could damage permanently the target. JP added that he was already observed during the first GDH experiment.

- Gordon pointed out that a two-pumping-chambers cell will allow to increase the gas volume to be polarized and the laser power.

- Metallic target chamber should be OK with end-caps.

- Many efforts at UVa are being focused on the glass-metal sealed.

- UVa will order a full scale two-pumping-chambers cell, fill it and test it. JP asked for another standard hybrid cell (3.5in pumping chamber diameter) for the JLab target lab.

- Wolfgang has been working on FEA of of temperature distribution on the target cell: Media:He3Target_Temp.pdf

  • Lasers:

- Laser procurement is an big issue. The COMET production was discontinued.

- Todd had contact with Laser Operations LLC. The system looks promising and cheap: here. Todd will order one to test and if all aspects are good more will be bought by JLab, ...

- Bill showed the laser system developed at UNH: 2.7kW narrowed laser (see his slides below).

  • Polarimetry:

- AFP will be used only for calibration: there will be significant polarization loss from this method with the new cell design.

- Pulsed NMR is under development.

- EPR can still be used.

- With convection, the polarization gradient between the pumping chamber and the target chamber will be significantly reduced. So polarimetry in the pumping chamber should be sufficient.

- A detailed study of the gas dynamics was recently published: Dolph, Singh et al.

  • Budget:

- Hall C should be able to start contributing to the A1n/d2n/pol3He target R&D in FY13.

  • Manpower:

- At JLab:

Zhiwen Zhao (UVa post-doc) is working part-time on the pol. 3He target. 
Jie Liu (UVa student) is also working part-time on the pol. 3He target.
Chunhua Chen (Hampton student on HKS) and Yawei Zhang (Rutgers student on E05-015) are working on the pol. 3He target during their free-time and will be gone soon.
Patricia (JLab) will be able to dedicate about a third of her time on the pol. 3He target R&D.

- At UVa:

Al Tobias, Vladimir Nelyubin and a student are working full time on the pol. 3He target system.

- W&M, Temple and UK expressed their interest to get involved and take some projects.

  • Task list:
   - Cell testing: polarization loss with different field gradients
   - Holding field design: look at the small field idea
   - Cell geometry optimization
   - Polarized gas dynamics
   - Max. polarization test: JLab need more lasers (at least 2 more)
   - Polarimetry cross calibration and optimization
   - kappa_0 measurement
   - Get a SUltra laser and test it.


  - from Patricia: talking points:  Media:Cpol3he_meeting_jan5_2012.pdf
  - from Gordon: Conceptual design for the A1n targets: Media:a1n_impromptu_target_present.pdf
  - from Bill: ex situ  3He polarizer system: Media:Xemed-polarizer.pdf

June 17-18, 2010

Workshop on High Luminosity Polarized Targets for the 12GeV Era (Joint Hall A & C Meeting)