Hall C Targets for 12 GeV

Silviu CovrigHall C

Hall C Users MeetingJanuary 23, 2010

• Cryogenic Targets LH2, LD2, (He)

• Polarized Targets

Standard Hall C 6 GeV LH2 Target

• Three loop design, at most 2 operational at any given time

• 7.5 liters/loop, 15 liters total

• 20 K, 1.5 atm, < 700 W

• 1-2 l/s, flow uncertainty 100%

• Cell length “on demand” (used 4, 8, 10, 15, 20, 25 cm long)

• 20 cm cell for GepIII had 20% yield reduction @ 80 A

• unsuitable for precision PV measurements

6GeV “Standard” LH2 Cells Designs

Beam direction

PV LH2 cells (G0 and Qweak)

G0 target designed @Caltech• horizontal 6 liters loop, 4.6 l/s, 20 cm cell• ran for 4 years in Hall C• 238 ppm nominal, best was 70 ppm• 0.4% yield reduction at 40A

Qweak target designed in Hall C

• vertical 54 liters loop, 15 l/s, 35 cm cell• needs to deliver 45 ppm• predicted 1.1% yield reduction @180A

12 GeV Hall C Approved Experiments

Experiment Target LH2, LD2

cm

Current

E12-06-101 8(4) 15-90

E12-06-104 10 50

E12-06-105 4 20-80

E12-06-107 15 80

E12-07-105 8 90

E12-07-102 20,40 10,85

E12-07-101 15 50-100

E12-09-011 8(4) 35-90

E12-09-017 10 50

E12-09-006 15,40 80

E12-09-002 10 15-50

+ 2 experiments that want a 40 cm 3He polarized target @5-30 A

There are 7 different lengths, we’d like to reduce the number to 4 (makes design and maintenance easier)

Question to USERS:

Is 20% yield drop @80A over 20 cm acceptable?

12 GeV Hall C Polarized Targets

- E12-06-110 and E12-06-121 want 40 cm of 3He polarized targets- Hall C didn’t have such a target for the 6 GeV program- The Hall A 3He target is a collaborative effort between 8 institutions- Would like to start a steering group to find a solution for Hall C (contact Patricia or

me)- Essentially two solutions:

1. Duplicate the Hall A target2. Built a new target based on the XeMed/UNH design

- NH3 polarized target ??? (UVA is interested in helping/building one, but there are no 12 GeV approved experiments in Hall C yet)

Hall A Polarized 3He Target

March 7, 2008March 7, 2008 Xemed LLCXemed LLC 99

XeMed/UNH Target loop ConceptXeMed/UNH Target loop Concept

• Compress polarized 3He and deliver to 40cm long titanium target cell• Commercial compressors achieve >3500 psi (238 bar)• Requires compression ratio ~16, immersion in magnetic field, rubidium-free gas leaving

polarizer, entrance and exit, <3% polarization loss

14 atm 200 atm

Recirculating at 1.0 scfm1 cm x 40 cm titanium target cell

Requires two ports, entrance and exit

Getter purifier? RGA?

Property Hall A UNHPolarization (%) 55 60Beam Current ( 15 100Pressure (atm) 10 200

Cell type Glass/sealed Ti/continuous flow

Spin “UP” time (h) 7 4Beam Relaxation (h-1) 41 0.1Laser Power (W) 150 1500-2500Thickness (cm-2) 1.07E+22 1E+24FOM (P2L ) 0.22E+36 0.55E+38