Possibility to increase intensity of polarized hydrogen target Dmitriy Toporkov Budker Institute of Nuclear Physics Novosibirsk, Russia Spin Physics Workshop June 2012, Gatchina, RUSSIA 1

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 2 Introduction Intensity limitation in ABS Source of polarized molecules High directivity capillary source of molecules Separating magnet for molecules Conclusion CONTENTS

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 3 M.Stancary et al. Intensities achieved from different ABS

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 4  q  n ) -1 = I 0 cos n  I foc. =  I 0  max 2 T (1-Att )  atomic fraction T – transmission factor 1 – Att – attenuation due to residual gas scattering  max 2 – maximum accepted solid angle Beam intensity from ABS

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 5 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, Possibility to increase intensity of polarized hydrogen target 6 Intensity of the H 2 molecular beam ( free beam ) T.Wise et al. NIMA 336(1993) 410

Possibility to obtain a polarized molecular hydrogen target 7 Shielding by the skimmer Two effect which may to provide saturation of the intensity Dmitriy Toporkov, Gatchina,

Possibility to obtain a polarized molecular hydrogen target 8 Dmitriy Toporkov, Gatchina,

Possibility to obtain a polarized molecular hydrogen target 9 Dmitriy Toporkov, Gatchina, Green – calculation Black – flow 0.2mbar*l/sec Red - flow 2mbar*l/sec

10  v/v max  0.25 v max  2*10 5 cm/sec  1.5* cm -2 this is from attenuation atomic beam by 300K residual gas For 20K beam temperature  should be larger For given    cm*sec I max = 1/(  *X) ~ 5*10 17 at/cm 2 For parallel beam and  v being the velocity spread Intra-beam scattering Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 11 Attenuation of the beam by residual gas - well understood process I(p) = I 0 *exp( -x*p/   p 0  ) Relative velocities of particles correspond room temperature

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 12 INJECTION OF BACKGROUND GAS AT DIFFERENT POSITION ATTENUATION OF THE BEAM IS DEPENDENT FROM THE POSITION OF THE GAS INJECTIOJN NOT MANY EXPERIMENTAL DATA AVAILABLE

13 Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 14

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 15 Magnetic properties of H 2 molecule Magnetic properties of D 2 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-D 2 molecule for m = -2, F= 2 equals ~  n, five time less than for o-H 2 molecule Orthohydrogen S = 1 L = 1, 3 … odd Parahydrogen S = 0 L= 0, 2 … even At room temperature concentration ratio in normal hydrogen C o-H2 /C p-H2 = 3:1 Magnetic moment of molecule is dependent on S and L. Magnetic moment of o-H 2 molecule for m= -2, F= 2 equals 5  n = 5*0.5* CGS=2.5*10 -3  B

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 16 Energy dependence of H 2 and D 2 molecule vs the magnetic field if 4 upper substates will be collected P z =0.5 and P zz =0.25 is expected if 3 upper substates will be collected P z =1 is expected

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 17 First (to my knowledge) spatial separation of o-H 2 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 H 2 mm Cross section of the magnet system

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 18 Diaphragm Oven slit Magnet Beam receiver Schematic view of the arrangement.

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 19 |В|=В 0 *(r/r mag ) N/2-1 Focusing properties of multipole magnets R(cm)

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 20 Suggested source of polarized molecules D=20 cm

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 21 Molecular flow through the long tube ~ L >> d Intensity in forward direction is the same as from the orifice, but total flow is less by a factor 3L/4d For further estimation L/d = 100, d=0.1  m

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 22 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, Possibility to increase intensity of polarized hydrogen target 23 The total area of the source is about 30 cm 2. Assuming geometrical transparency of 50% this area should contain 2*10 11 capillaries. If we set a flux through a single capillary 1*10 10 mol/sec the density of the molecules before a capillary should be in the range of 1*10 18 mol/cm 3. Total flux of molecules 2*10 21 mol/sec

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 24 Monte Carlo simulation of flow through the cylindrical channel degree L/d=100

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target Radial density distribution at 100 cm distance from the capillary with d  m L/d=100 Arb. unit

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 26 Number of poletips – 32 Magnetic poletip field 4 T

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 27 Spatial distribution of molecules at the exit of the separating magnet from a single capillary

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 28 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* The fraction of the focusing molecules in the flow is ¼ ( ¼ is p-H 2 molecules, 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*10 18 mol/sec Results of simulation

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 29 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, Possibility to increase intensity of polarized hydrogen target 30 We have some superconducting sextupole magnets installed in cryogenic Atomic Beam Source Nearest plans

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 31 Some spare magnets can be used to test the idea to focus hydrogen molecules Nearest plans

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 32 Pumping speed of cryosurface at given temperature is different for hydrogen and deuterium gas Attenuation of hydrogen beams by the rest gas Pressure, bar Intensity of the atomic beam Temperature, K

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 33 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, Possibility to increase intensity of polarized hydrogen target 34 Intensity measurement

Dmitriy Toporkov, Gatchina, Possibility to increase intensity of polarized hydrogen target 35 Conclusion Intensities of polarized beams from the Atomic Beam sources seems have reached it’s limit of about at/sec. Proposed source of polarized ortho-hydrogen (o-H 2 ) 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.