The HD target JLab12 Collaboration Meeting Annalisa D’Angelo Alessia Fantini, Carlo Schaerf and Valentina Vegna University of Rome Tor Vergata and INFN Roma Tor Vergata Roma- October 19th 2009

Outline - Principles of HD frozen-spin target production and properties of Hydrogen isotopes molecules - Optimization of orto-H2 and para-D2 concentrations HD gas distillation HD gas analysis  gas chromatography high resolution HD gas analysis  Raman Scattering Improvements on Raman Set-up Target condensation and NMR set-up Target polarization  New Building construction Target transportation and New In-beam cryostat

Determination of orto-H2 and para-D2 concentrations in HD gas using Raman Scattering HD frozen-spin target advantages: Fraction of free protons exceeds any other polarized target  High dilution factors H and D may be independently polarized and their polarization may be independently reversed  proton and neutron polarization H and D may reach a high degree of polarization: 95 % for H 70% for D In the frozen-spin condition targets may be cold-transported, stored and used in beams under simple environment: (B = 7 Tesla ,T=4k B=1 Tesla , T=0.5K) storage experiment HD frozen-spin target main disadvantage: - long production cycles  R&D

Why HD : properties of hydrogen isotopes Homo-nuclear molecules: H2 (D2) wave-functions must be symmetric (anti-symmetric) under nuclear exchange Hetero-nuclear molecules (HD) do not obey any symmetry constraint Nuclear Exchange  space inversion for electrons and nuclear spatial coordinates e (-1)L symmetric in the ground state (L=0) V symmetric in the ground state ( =0) Rotational levels ER= b0 J(J+1) symmetry is given by (-1) J Always symmetric in the ground state Nuclear spins: H2 (Ip =1/2) Spins couple to I = 0 (anti-symmetric) I=1 (symmetric) D2 (Id =1) Spins couple to I = 0,2 (symmetric) I=1 (anti-symmetric) J= even Symmetric J = odd Anti-symmetric The H2 and D2 molecules are in I=0 ground state and may not be polarized I=1 molecular states may be polarized - not the molecular ground states - associated to J odd rotational states - meta-stable H2 wave-function must be anti-symmetric : I = 0 couples to J even (para-H2) I=1 couples to J odd (orto-H2) D2 wave-function must be symmetric : I = 0,2 couples to J even (orto-D2) I=1 couples to J odd (para-D2) Nuclei in HD molecules may be polarized in the ground state

1) Brute force: High field/low temperature HD frozen-spin target principle of operation: brute force and a gentle touch 1) Brute force: High field/low temperature By A. Sandorfi High field B=15 -17 T and low temp T=10-15 mK align spins with magnetic field Maximum equilibrium polarization PH = 0.91-0.95 PD = 0.3

2) Gentle touch: longitudinal relaxation time switch mechanisms. HD frozen-spin target principle of operation: brute force and a gentle touch 2) Gentle touch: longitudinal relaxation time switch mechanisms. T1H = minutes if orto-H2 concentration10-3 T1H = months if orto-H2 concentration10-6 H D Direct spin-lattice relaxation is suppressed T1H increases while orto-H2 concentration in HD decreases T1H and T1D very high for pure HD gas T1H depends on orto-H2 concentration in HD Cross-relaxation spin-spin interaction spin-lattice relaxation is suppressed H Efficient spin-lattice relaxation H Para-H2 I=0,J=0 ground state Orto-H2 I=1,J=1 impurities T1H spin-lattice relaxation switch Decay 6.8 days T=172 K AGING

2) Gentle touch: longitudinal relaxation time switch mechanisms. HD frozen-spin target principle of operation: brute force and a gentle touch 2) Gentle touch: longitudinal relaxation time switch mechanisms. H D Direct spin-lattice relaxation is suppressed T1D depends on para-D2 concentration in HD T1D increases while para-H2 concentration in HD decreases T1H and T1D very high for pure HD gas Cross-relaxation spin-spin interaction spin-lattice relaxation is suppressed D Efficient spin-lattice relaxation D Para-D2 I=1,J=1 impurities Orto-D2 I=0,2 J=0 ground state T1D spin-lattice relaxation switch Decay 18.6 days T=86 K D AGING

HD polarization: relaxation time T1H

HD distillation Commercial HD contains  98% HD 1.5% H2 ≤0.5% D2 Distillation process developed By Steve Whinsnant @ USC 12 moles in the batch

HD distillery operation 6-7 moles may be distilled in three weeks reducing the orto-H2 and para-D2 contaminants by a factor 10 By Steve Whinsnant @ USC

Gas chromatography: measurement of the thermal conductivity difference with respect of Neon gas carrier, as a function of retention time Varian CP-3800 GC Retention time is a function of the molecular mass and spin. Double distillation is necessary to reduce the contamination content by two orders of magnitude. The GC resolution limit is  0.1% By Steve Whinsnant @ USC

Problems HD gas stored in high pressure tanks tends to dissociate and recombine in H2 and D2 species, at a rate of 0.14% /month There are indications that after aging the para-H2  orto-H2 conversions occurs with a very long time constant in normal conditions. Accurate measurement of orto-H2 and para-D2 content in the HD is highly desirable

Raman spectroscopy: laser scattering from rotational states Connects orto- to orto- and para- to para- molecular states J=2

Raman set-up Argon Ion Laser Beam expander

Concentration Measurement < 0.5% D2 in H2  (cm-1)

Exponential dependence from Raman lines intensity: Temperature dependence Partition function I0 = Laser Intensity A() = spectral response function f(J) = an-harmonicity correction = anisotropic matrix element N = total number of molecules gs(J) = nuclear spin multiplicity Constant C where Exponential dependence from 1/ gas Temperature CN and T may be extracted from a fit to data

Dominant H2   J Iexp (c/s) Iexp 467.65 0.21 1 1391.5 0.2 2 200.74 3 132.15  

Main H2 gas content Log A = ( 2.764  0.002 ) counts/s J Iexp(J)Iexp (counts/s) Ifit(J)Iexp (J) (counts/s) 467.650.2 467.29 0.1 1 1391.5 0.2 1391.6 0.2 2 200.74 0.2 201.53 0.03 3 132.15 0.2 131.44 0.02 4 - 4.9731 0.0009 5 0.9014 0.0001 6 (0.9766  0.0002)10-2 7 (0.5155  0.0001)10-3 E(J)/KB (K-1) Log A = ( 2.764  0.002 ) counts/s T = (286.4  0.2) K Itot exp = (2192.1 0.8) counts/s Itot fit = (2197.7 0.4) counts

Extraction of analysis for different H2 species J para-H2 CNeven/ CNtot= 0.25090.0005 orto-H2 J CNodd/ CNtot= 0.75000.0005 J

D2 contaminant J (counts/s) 1 2 3 4 Iexp(J)Iexp 1.27 0.16  (cm-1) J Iexp(J)Iexp (counts/s) 1 1.27 0.16 2 2.15 0.15 3 0.68 0.12 4 0.35 0.12  (cm-1)  (cm-1)  (cm-1)

D2 gas content Log A = ( -1.1  0.1 ) counts/s T = (294  30) K J Iexp(J)Iexp (counts/s) Ifit(J)Iexp (J) (counts/s) - 1.9920 0.21 1 1.270.16 1.34 0.21 2 2.15 0.14 2.13 0.23 3 0.680 0.12 0.57 0.06 4 0.34 0.12 0.43 0.04 5 0.060 0.006 6 0.024 0.002 7 0.0017  0.0002 Log A = ( -1.1  0.1 ) counts/s T = (294  30) K E(J)/KB (K-1) I tot= (6.57 0.71) counts/s

D2/H2= (0.00290.0003) H2 temperature Fit I tot= (6.460.69) C/s D2 temperature

Extraction of analysis for different D2 species J orto-D2 CNeven/ CNtot= 0.660.03 para-D2 J CNodd/ CNtot= 0.330.03 CND2/ CNH2 = (0.0030.001) J

Progress on Raman Analysis: Raman spectroscopy works. Sensitivity is being upgraded from 10-4 to 10-5: New Laser  15 W on the green line repaired New cell with lower inner volume and non-magnetic windows done New beam expander mounted Second mirror available to be mounted PM instead of CCD will be done in November New measurements: - 0.3% D2 in H2 being repeated to check improvements Commercial HD gas analysis Absolute normalization: 50% H2-HD, H2 -D2, H2-HD mixtures – precise gauge. Real HD sample – sent from JLAB  next weeks

HD-ice target production: condensation Target :  = 15 mm x50 mm Material: solid HD HD Gas is condensed in a production Dewar were equilibrium temperature NMR is also performed. It has been found that HD must be condensed at HIGH PRESSURE (30 atm) to avoid formation of holes in the HD crystal. The Rome group has been asked to develop a new production Dewar allowing: High pressure production of HD NMR measurements with sweeping frequency and fixed magnetic field

HD-ice target production: polarization HDice Target Lab: renovated test lab annex condense HD gas  liquid  solid at 16 K calibrate pol- NMR at T=2 K and B= 0.2 T transfer to dilution refrigerator & polarize at 15-17 T and 12 mK hold at high-field low temp. for > 3 months transfer to 8 T/1.6 K storage Cryostat

HD-ice target production: run the experiment Hall-B move to Hall B transfer to In-Beam Cryostat (IBC) move spins HD as needed roll IBC into Clas run the experience P(H) = 75% P(D)=40% Dilution factors: ½ 1 T1 (1/e relaxation time  years)

HD ice Time Line: 1st Occupancy of HDice Lab: Nov/09 IBC test with polarized HD (in HDice Lab): July/10 IBC installed in CLAS/ Hall-B: Sept/10 Start of g14/E06-101( ) 27/9/10 Test of Apr /10 Start of ET- 1/E08 -021/015 07/Nov/11