E08-027

1. E08-027 Resource Planning Meeting March 3, 2008 JLab A110

2. Overview The inclusive nucleon SSF g1 and g2 are measured over wide range, but remains unmeasured below Q2=1.3 GeV2. The missing piece of the JLab Spin Physics Program. Motivations • g2p is central to our understanding of nucleon structure. • BC Sum Rule violation suggested at large Q2. • State of the Art PT calculations fail for neutron spin polarizability LT. • Knowledge of is a leading uncertainty in Hydrogen Hyperfine calculations. • Resonance Structure, in particular the ¢(1232). • Also a leading uncertainty in longitudinal measurements of (Hall B EG1, EG4). This Experiment Measure in the resonance region for 0.02 < Q2 < 0.4 using the Hall A septa and the polarized ammonia target.

3. Installation Needed Five Tesla Polarized Ammonia Target • Upstream Chicane and Supports • Local Beam Dump • Slow Raster and Basel SEM Septa Magnets • Vacuum coupling not needed

4. Target Target Outer Vacuum Chamber (OVC) : Any existing can will be sufficient for g2p. One new Sane can, two old Slac cans. Need to locate both SLAC cans. Magnet and Controls : onsite at JLab Microwaves: two tubes and one power supply at JLab. 3 tubes and 2 power supplies at UVA Frequency and power measurement : UVA has two systems. JLab has atleast one. NMR system : JLab has 4-5 Q-meter boxes. Uva has an additional 11. Complete computer control systems exist at both JLab and UVa. Pumps: Complete set onsite. Can utilize spares from UVA or Hall B, but requires time to swap. Need to service the primary set before run to reduce need for backup. Instrumentation : Target movers. Remote control for pumps. All exists at JLab. Need new cabling from Counting House Target Inserts: 4 at UVA. All being refurbished for SANE. Cryogenics : Hall C Dewar. Need 4K Helium spigot near target. Possible to use a 15K line? Also need liquid Nitrogen. Are our cryo needs compatible with QWEAK? Ammonia: Need fresh material. $210/liter of 15NH3. $200/hr to irradiate. Issue : overhead clearance for target insertion. Need more than 6 feet.

5. Target Platforms 3 Target Platforms in Hall C 1) Target Support Ring Platform. 2) Helium Dewar, computer rack, electronics, ¹-wave 3) Roughing Pumps. This platform is permanent part of Hall C. Possible to locate these pumps on floor? Otherwise need new platform design and fabrication.

6. Chicane 10 m 4 m Moller EP Target center • Chicane Design : Jay Benesh (JLab CASA) • Two upstream Dipoles, one with vertical D.O.F. • Reuse the dipoles from the HKS experiment. • Beam dump is above beamline. • Below may be possible ( being investigated ) One of the HKS Magnets used for Hall C “minibend”. Need to locate replacement. Talking to Jay

7. Chicane • Remove French bench • Install fixed support • Install dipole and associated instrumentation • Install movable stand • Install second dipole and instrumentation • Connect SEM to scattering chamber Not likely we can use either of the stands or hydraulics from Hall C

8. Beam Dump • Proposal design • 2 helium bag with Al windows • Concrete blocks • Option to go down is being investigated • Smaller dump, better control of radiation. • Room issue between spectrometer • Background issue ( needs to be closer from the target )

9. Beam Dump • Remove beamline section • Install bags with Al windows • Stack concrete blocks and install dump • No Cooling needed We can reuse the concrete block, steel and shielding from SANE Can not reuse SANE He bag (<4 degree). Deflection angle too big

10. Other Beamline Components Secondary Emission Monitor (SEM) Slow Raster Movable Beam Pipe with additional bcm/bpms Standard Beam pipe for “straight-thru” operation Hall C Beam Girder : Holds Harp, SEM and BPM/BCM

11. Septa: 4 Options Two Cryogenic Septa Advantages: Scenario assumed in proposal. Ideal for physics. Drawbacks: Requires Septa repair, cryo during QWEAK • Single Cryogenic Septa • Advantages: Still cover Q2 range of proposal • Drawbacks: Lose systematic cross-check. Need additional beamtime. • The Warm Septa • Advantages: Avoid repairing the cold septa. Reduce our total cryo-load. • Drawbacks: Largest negative impact on physics goals. • Needs to be modified to be compatible with chicane. • Warm Septa run + a Separate “HRS only” run • Advantages: Achieves Q2 coverage of proposal (and a bit more). • Drawbacks: Significant amount of time to deinstall warm septa • and move the target back from its retracted position.

12. Cold septa design Two Cryogenic Septa • Need to leave small gap between Septa for chicaned beam to pass. • Target moved further upstream by 60 cm • Exit pipe to be replaced by small helium bag

13. Two Cold Septa Require Cold Septa Data Taking 15.7 Overhead 8.4 Achieves all proposal goals Total Days 24.1

14. 1 Cold Septa (Left Only) Require Cold Septa Data Taking 25.2 Overhead 8.4 Requires additional 10 days No Cross Check Total Days 33.6

15. Warm Septa What we can do with Warm Septa Data Taking 8.6 Overhead 6.4 Reduces Max Q2 from 0.32 to 0.14 GeV2 Total Days 15.0 Compatible with Chicane?

16. Warm Septa • Being investigated • Transverse target requirements need to be checked and adapted

17. Warm Septa+HRS only HRS Only Warm Septa Data Taking 16.3 Achieves all physics goals++ of proposal Overhead 8.9 But requires additional month (?) of configuration change Total Days 25.2

18. Impact on Physics

19. Open Issues Cold Septa compatible with Qweak? Warm Septa would have to be modified to work with Chicane. What investment in time/effort is needed to fix the right Septa? 4) Single movable beam pipe, or 2 pipes?