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Possibility to increase intensity of polarized hydrogen target
Dmitriy ToporkovDmitriy Toporkov
Budker Institute of Nuclear PhysicsBudker Institute of Nuclear Physics
Novosibirsk, RussiaNovosibirsk, Russia
Spin Physics Workshop Spin Physics Workshop 24-28 June 2012, Gatchina, RUSSIA
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Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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• Introduction• Intensity limitation in ABS • Source of polarized molecules• High directivity capillary source of molecules• Separating magnet for molecules• Conclusion
CONTENTS
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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M.Stancary et al.
Intensities achieved from different ABS
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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0( ) ( 1)cos
2nQdI n
d
n )-1
= I0cosn
Ifoc.= I0 max2 T (1-Att )
atomic fraction
T – transmission factor1 – Att – attenuation due to residual gas scatteringmax
2 – maximum accepted solid angle
Beam intensity from ABS
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Factors limiting the intensity from ABS
• Increasing a size of the source of atoms with increasing throughput • Intra-beam scattering• Pressure bump in the ABS• Attenuation by the residual gas
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Intensity of the H2 molecular beam ( free beam )
T.Wise et al. NIMA 336(1993) 410
Possibility to obtain a polarized molecular hydrogen target
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Shielding by the skimmer
Two effect which may to providesaturation of the intensity
Dmitriy Toporkov, Gatchina, 24-28.06.2012
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Possibility to obtain a polarized molecular hydrogen target
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Possibility to obtain a polarized molecular hydrogen target
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Green – calculationBlack – flow 0.2mbar*l/secRed - flow 2mbar*l/sec
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v/vmax 0.25 vmax 2*105 cm/sec
1.5*10-14cm-2 this is from attenuation atomicbeam by 300K residual gas
For 20K beam temperature should be largerFor given cm*secImax = 1/(*X) ~ 5*1017 at/cm2
For parallel beam and v being the velocity spread
Intra-beam scattering
Dmitriy Toporkov, Gatchina, 24-28.06.2012
10Possibility to increase intensity of polarized hydrogen target
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Attenuation of the beam by residual gas - well understood process
I(p) = I0*exp( -x*p/p0 )
Relative velocitiesof particles correspond roomtemperature
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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INJECTION OF BACKGROUND GAS AT DIFFERENT POSITION
ATTENUATION OF THE BEAM ISDEPENDENT FROM THE POSITIONOF THE GAS INJECTIOJN
NOT MANY EXPERIMENTAL DATAAVAILABLE
13Dmitriy Toporkov, Gatchina, 24-28.06.2012
13Possibility to increase intensity of
polarized hydrogen target
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Magnetic properties of H2 molecule
Magnetic properties of D2 molecule
Total spin S = 2, 0 L = 0, 2 … even S = 1 L = 1, 3 … odd
Magnetic moment of molecule is dependent on S and L.Magnetic moment of o-D2 molecule for m = -2, F= 2 equals ~n , five time less than for o-H2 molecule
Orthohydrogen S = 1 L = 1, 3 … oddParahydrogen S = 0 L= 0, 2 … evenAt room temperature concentration ratio in normal hydrogen C o-H2 /Cp-H2 = 3:1
Magnetic moment of molecule is dependent on S and L.Magnetic moment of o-H2 molecule for m= -2, F= 2 equals 5n = 5*0.5*10-23 CGS=2.5*10-
3B
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Energy dependence of H2 and D2 molecule vs the magnetic field if 4 upper substates will be collected
Pz=0.5 and Pzz=0.25 is expected
if 3 upper substates will be collected Pz=1 is expected
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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First (to my knowledge) spatial separation of o-H2 molecules in inhomogeneous magnetic field have been done by Frisch R. and Stern О. [F r i s c h R. und S t e r n О., Ztschr. f. Phys., 85, 4, 1933].
Magnetic separation of the beam of H2
mm
Cross sectionof the magnet system
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Diaphragm
Oven slit
Magnet
Beam receiver
Schematic view of the arrangement.
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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|В|=В0*(r/rmag)N/
2-1
Focusing properties of multipole magnets
0 5 10 R(cm)
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Suggested source of polarized molecules
D=20 cm
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Molecular flow through the long tube
~ L >> d
Intensity in forward direction is the same as fromthe orifice, but total flow is less by a factor 3L/4d
For further estimation L/d = 100, d=0.1m
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Regular microporous membrane with pores of 0.3 m in diameter and 30 m thickness have a geometrical transperancy of about 70% could be fabricated by the method of deep X-ray lithography [G.N.Kulipanov et al. Nucl. Instr. And Meth. A359, 404(1995)]
Capillary ring array D = 20cm, width = 0.5cm
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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The total area of the source is about 30 cm2. Assuming geometrical transparency of 50% this area should contain 2*1011capillaries. If we set a flux through a single capillary 1*1010mol/sec the density of the molecules before a capillary should be in the range of1*1018mol/cm3. Total flux of molecules 2*1021mol/sec
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Monte Carlo simulation of flow through the cylindrical channel
degree
L/d=100
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
Radial density distribution at 100 cm distance from the capillary with d m
L/d=100
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Number of poletips – 32Magnetic poletip field 4 T
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Spatial distribution of molecules at the exit of the separating magnet from a single capillary
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Monte-Carlo simulation has shown that the fraction of molecules from a single capillary that reached an entrance aperture of the magnet and focused to its axis has a value of 2.3*10-3. The fraction of the focusing molecules in the flow is ¼ ( ¼ is p-H2molecules, ¼ is defocused and ¼ has a magnetic moment close to zero).Estimated fraction of the focusing molecules is about 0.6*10-3 of the total flux or 1*1018 mol/sec
Results of simulation
Dmitriy Toporkov, Gatchina, 24-28.06.2012
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Formation of the molecular beam with highest directivity
Realization of huge pumping system
Preservation of the nucleon polarization during the transportation of molecules
Key points
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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We have some superconducting sextupole magnets installed in cryogenic Atomic Beam Source
Nearest plans
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Some spare magnets can be used to test the idea to focus hydrogen molecules
Nearest plans
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Pumping speed of cryosurface at given temperatureis different for hydrogen and deuterium gas
Attenuation of hydrogen beamsby the rest gas
Pressure, bar
Temperature, K
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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A magnetically focused molecular beam of ortho-water
p.319
The 0.3 m long, 1 mm internal radius magnet achieves a polepiece tip field of 1.1 T using NdFeB permanent magnets and Permendur 49 polepieces.
T. Kravchuk et al.,
Dmitriy Toporkov, Gatchina, 24-28.06.2012
Possibility to increase intensity of polarized hydrogen target
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Intensity measurement
Dmitriy Toporkov, Gatchina, 24-28.06.2012
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Conclusion• Intensities of polarized beams from the Atomic
Beam sources seems have reached it’s limit of about
1017at/sec.
• Proposed source of polarized ortho-hydrogen (o-H2 )
molecules probably will provide intensity by order of
magnitude higher. For deuterium gas situation is harder du
to the smaller magnetic moment of the molecule.
• An opening questions are preservation of polarization
of molecules under injection into the storage cell and
realization of huge differential pumping system needed
to get good vacuum condition.
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