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Polarized target

May 08, 2024

The polarized targets are used as fixed targets in scattering experiments. In high energy physics they are used to study the nucleon spin structure of simple nucleons like protons, neutrons or deuterons. In deep inelastic scattering the hadron structure is probed with electrons, muons or neutrinos. Using a polarized high energy muon beam, for example, on a fixed target with polarized nucleons it is possible to probe the spin dependent part of the structure functions.[1][2]

In the simple parton model the nucleon consists of quarks and gluons and their interaction is governed by quantum chromodynamics. An alternative method to the fixed targets is to use two colliding polarized beams. Several institutes and laboratories work in this field.[3][4][5][6][7][8]

An international workshop on "Polarized Sources, Targets and Polarimetry" takes place every two years.[9][10][11][12][13][14]

The nuclear spins in the solid targets are polarized with dynamic nuclear polarization method typically in 2.5 or 5 T magnetic field.[15][16]

The magnetic field can be generated with a superconducting magnet filled with liquid helium. The more traditional iron magnets are not preferred due to their large mass and limited geometrical acceptance for the produced particles. The target polarization during the experiment is determined with the nuclear magnetic resonance method. The integrated enhanced NMR-signals are compared to the signals taken in superfluid helium-4 bath at well known calibration temperatures around 1 K, where the spin magnetization follows the Curie law and the nuclear polarization can be calculated from the temperature by using the Brillouin function. During the polarization build up a microwave generator is used to pump the paramagnetic centers in the target material close to the electron spin resonance frequency (about 70 GHz in 2.5 T field).

In the helium-3 gas targets[17][18][19] optical pumping is used to polarize the nucleons.

In the frozen spin targets low temperatures are needed to preserve the polarization for long data taking periods (for the highest possible integrated luminosity) and to reach maximum nuclear polarization for the best figure of merit. Usually a dilution refrigerator with high cooling power is used to reach temperatures below 300 mK during the polarization build up and below 50 mK in frozen spin mode.[20][21][22]

To preserve the paramagnetic centers in the target material it has to be kept all the time at cryogenic temperatures typically below 100 K. A horizontal dilution cryostat with the possibility to load directly the target material into the helium-3/4 mixing chamber from a liquid nitrogen bath is needed for this reason. While the beam should interact with the target material scattering from the target construction materials is not desired. This leads to an additional requirement of small material budget in terms of radiation length. Thin and low density construction materials are used for this reason in the region of the incoming beam and the scattering products.

The properties of a good polarized target material[4] are high number of polarizable nucleons compared to the total amount of nucleons, high polarization degree, short polarization build up time, slow polarization loss rate in frozen spin mode, good resistance against radiation damage and easy handling of the target material. For the dynamic nuclear polarization the material has to be doped with free radicals. Two different ways are usual: chemical doping by mixing with free radicals and creation of F-centers by irradiation in an intensive electron beam. Commonly used target materials are butanol, ammonia,[23][24][25] lithium hydrides [26] and their deuterated counterparts. A very interesting material is hydrogen deuteride, because it has the maximal content of polarizable nucleons. High proton polarizations have been reached in a large naphthalene single crystal using optically excited triplet states of fully deuterated pentacene guest molecules.[27] at temperatures around 100 K and magnetic field of 0.3 T. Hyperpolarized carbon-13 has been studied for medical imaging applications [28]

References edit

  1. ^ E. Leader (2001). "Spin in Particle Physics". Cambridge University Press. ISBN 0521352819.
  2. ^ S. D. Bass (2008). "The Spin Structure of the Proton". World Scientific Publishing. ISBN 9812709479
  3. ^ PSI
  4. ^ a b Ruhr-Universität Bochum Polarized Target Group
  5. ^ Yamagata University, Research Group for Quark Nuclear Physics
  6. ^ University of Virginia Spin Physics Group,University of Virginia Polarized Target Group
  7. ^ Polarized Target Bonn
  8. ^ N. A. Bazhanova; B. Bendab; N. S. Borisovc; A. P. Dzyubakd; G. Durandb; L. B. Golovanove; G. M. Gurevichf; A. I. Kovaleva; A. B. Lazarevc; F. Leharb; A. A. Lukhanind; A. B. Neganovc; S. V. Topalovf; S. N. Shilovc; Yu. A. Usov (1996). "A movable polarized target for high energy spin physics experiments". Nuclear Instruments and Methods in Physics Research A. 372 (3): 349–351. Bibcode:1996NIMPA.372..349B. doi:10.1016/0168-9002(95)01307-5.
  9. ^ XIth International Workshop on Polarized Sources and Targets, November 14-17, 2005, Tokyo, Japan
  10. ^ XIIth International Workshop on Polarized Sources, Targets & Polarimetry, September 10-14, 2007, New York, USA
  11. ^ XIIIthInternational Workshop on Polarized Sources, Targets & Polarimetry, September 7 - 11, 2009, Ferrara, Italy
  12. ^ XIVth International Workshop on Polarized Sources, Targets & Polarimetry, September 12 - 18, 2011, St. Petersburg, Russia
  13. ^ The 2013 International Workshop on Polarized Sources, Targets & Polarimetry, September 9-13, 2013, Charlottesville, USA
  14. ^ The 2015 International Workshop on Polarized Sources, Targets & Polarimetry, September 14-18, 2015, Bochum, Germany
  15. ^ D. G. Crabb; W. Meyer (1997). "Solid Polarized Targets for Nuclear and Particle Physics Experiments". Annual Review of Nuclear and Particle Science. 47: 67–109. Bibcode:1997ARNPS..47...67C. doi:10.1146/annurev.nucl.47.1.67.
  16. ^ A. Dael; D. Cacaut; H. Desportes; R. Duthil; B. Gallet; F. Kircher; C. Lesmond; Y. Pabot; J. Thinel (1992). "A superconducting 2.5 T high accuracy solenoid and a large 0.5 T dipole magnet for the SMC target". IEEE Transactions on Magnetics. 28 (1): 560–563. Bibcode:1992ITM....28..560D. doi:10.1109/20.119937.
  17. ^ Thomas Jefferson National Accelerator Facility, Hall A Helium-3 Target
  18. ^ H. Middleton; G. D. Cates; T. E. Chupp; B. Driehuys; E. W. Hughes; J. R. Johnson; W. Meyer; N. R. Newbury; T. Smith; A. K. Thompson (1993). "The SLAC high‐density 3He target polarized by spin‐exchange optical plumbing" (PDF). AIP Conference Proceedings. 293: 244–252. doi:10.1063/1.45130. hdl:2027.42/87509.
  19. ^ St. Goertz; W. Meyer; G. Reicherz (2002). "Polarized H, D, and 3He Targets for Particle Physics Experiments". Progress in Particle and Nuclear Physics. 49 (2): 403–489. Bibcode:2002PrPNP..49..403G. doi:10.1016/S0146-6410(02)00159-X.
  20. ^ T. O. Niinikoski (1971). "A horizontal dilution refrigerator with very high cooling power". Nuclear Instruments and Methods. 97 (1): 95–101. Bibcode:1971NucIM..97...95N. doi:10.1016/0029-554X(71)90518-0.
  21. ^ S. Isagawa; S. Ishimoto; A. Masaike; K. Morimoto (1978). "A horizontal dilution refrigerator for polarized target". Nuclear Instruments and Methods. 154 (2): 213–218. Bibcode:1978NucIM.154..213I. doi:10.1016/0029-554X(78)90401-9.
  22. ^ T. O. Niinikoski (1982). "Dilution refrigerator for a two-litre polarized target" (PDF). Nuclear Instruments and Methods in Physics Research. 192 (2–3): 151–156. Bibcode:1982NucIM.192..151N. doi:10.1016/0029-554X(82)90817-5.
  23. ^ T. O. Niinikoski; J.-M. Rieubland (1979). "Dynamic nuclear polarization in irradiated ammonia below 0.5 K". Physics Letters A. 72 (2): 141–144. Bibcode:1979PhLA...72..141N. doi:10.1016/0375-9601(79)90673-X.
  24. ^ D. G. Crabb; C. B. Higley; A. D. Krisch; R. S. Raymond; T. Roser; J. A. Stewart; G. R. Court (1990). "Observation of a 96% Proton Polarization in Irradiated Ammonia". Physical Review Letters. 64 (22): 2627–2629. Bibcode:1990PhRvL..64.2627C. doi:10.1103/PhysRevLett.64.2627. PMID 10041768.
  25. ^ W. Meyer (2004). "Ammonia as a polarized solid target material - a review". Nuclear Instruments and Methods in Physics Research A. 526 (1–2): 12–21. Bibcode:2004NIMPA.526...12M. doi:10.1016/j.nima.2004.03.145.
  26. ^ J. Ball (2004). "Thirty years of research with lithium compounds in Saclay". Nuclear Instruments and Methods in Physics Research A. 526 (1–2): 7–11. Bibcode:2004NIMPA.526....7B. doi:10.1016/j.nima.2004.03.144.
  27. ^ T. R. Eichhorn; M. Haag; B. van den Brandt; P. Hautle; W. Th. Wenckebach (2013). "High proton spin polarization with DNP using the triplet state of pentacene-d14". Chemical Physics Letters. 555: 296–299. Bibcode:2013CPL...555..296E. doi:10.1016/j.cplett.2012.11.007.
  28. ^ M. S. Vindinga; C. Laustsena; I. I. Maximovd; L. V. Søgaardb; J. H. Ardenkjær-Larsene; N. Chr. Nielsena (2013). "Dynamic nuclear polarization and optimal control spatial-selective 13C MRI and MRS". Journal of Magnetic Resonance. 227: 57–61. Bibcode:2013JMagR.227...57V. doi:10.1016/j.jmr.2012.12.002. PMID 23298857.

External links edit

  • COMPASS experiment at CERN

May 08, 2024
polarized, target, polarized, targets, used, fixed, targets, scattering, experiments, high, energy, physics, they, used, study, nucleon, spin, structure, simple, nucleons, like, protons, neutrons, deuterons, deep, inelastic, scattering, hadron, structure, prob. The polarized targets are used as fixed targets in scattering experiments In high energy physics they are used to study the nucleon spin structure of simple nucleons like protons neutrons or deuterons In deep inelastic scattering the hadron structure is probed with electrons muons or neutrinos Using a polarized high energy muon beam for example on a fixed target with polarized nucleons it is possible to probe the spin dependent part of the structure functions 1 2 In the simple parton model the nucleon consists of quarks and gluons and their interaction is governed by quantum chromodynamics An alternative method to the fixed targets is to use two colliding polarized beams Several institutes and laboratories work in this field 3 4 5 6 7 8 An international workshop on Polarized Sources Targets and Polarimetry takes place every two years 9 10 11 12 13 14 The nuclear spins in the solid targets are polarized with dynamic nuclear polarization method typically in 2 5 or 5 T magnetic field 15 16 The magnetic field can be generated with a superconducting magnet filled with liquid helium The more traditional iron magnets are not preferred due to their large mass and limited geometrical acceptance for the produced particles The target polarization during the experiment is determined with the nuclear magnetic resonance method The integrated enhanced NMR signals are compared to the signals taken in superfluid helium 4 bath at well known calibration temperatures around 1 K where the spin magnetization follows the Curie law and the nuclear polarization can be calculated from the temperature by using the Brillouin function During the polarization build up a microwave generator is used to pump the paramagnetic centers in the target material close to the electron spin resonance frequency about 70 GHz in 2 5 T field In the helium 3 gas targets 17 18 19 optical pumping is used to polarize the nucleons In the frozen spin targets low temperatures are needed to preserve the polarization for long data taking periods for the highest possible integrated luminosity and to reach maximum nuclear polarization for the best figure of merit Usually a dilution refrigerator with high cooling power is used to reach temperatures below 300 mK during the polarization build up and below 50 mK in frozen spin mode 20 21 22 To preserve the paramagnetic centers in the target material it has to be kept all the time at cryogenic temperatures typically below 100 K A horizontal dilution cryostat with the possibility to load directly the target material into the helium 3 4 mixing chamber from a liquid nitrogen bath is needed for this reason While the beam should interact with the target material scattering from the target construction materials is not desired This leads to an additional requirement of small material budget in terms of radiation length Thin and low density construction materials are used for this reason in the region of the incoming beam and the scattering products The properties of a good polarized target material 4 are high number of polarizable nucleons compared to the total amount of nucleons high polarization degree short polarization build up time slow polarization loss rate in frozen spin mode good resistance against radiation damage and easy handling of the target material For the dynamic nuclear polarization the material has to be doped with free radicals Two different ways are usual chemical doping by mixing with free radicals and creation of F centers by irradiation in an intensive electron beam Commonly used target materials are butanol ammonia 23 24 25 lithium hydrides 26 and their deuterated counterparts A very interesting material is hydrogen deuteride because it has the maximal content of polarizable nucleons High proton polarizations have been reached in a large naphthalene single crystal using optically excited triplet states of fully deuterated pentacene guest molecules 27 at temperatures around 100 K and magnetic field of 0 3 T Hyperpolarized carbon 13 has been studied for medical imaging applications 28 References edit E Leader 2001 Spin in Particle Physics Cambridge University Press ISBN 0521352819 S D Bass 2008 The Spin Structure of the Proton World Scientific Publishing ISBN 9812709479 PSI a b Ruhr Universitat Bochum Polarized Target Group Yamagata University Research Group for Quark Nuclear Physics University of Virginia Spin Physics Group University of Virginia Polarized Target Group Polarized Target Bonn N A Bazhanova B Bendab N S Borisovc A P Dzyubakd G Durandb L B Golovanove G M Gurevichf A I Kovaleva A B Lazarevc F Leharb A A Lukhanind A B Neganovc S V Topalovf S N Shilovc Yu A Usov 1996 A movable polarized target for high energy spin physics experiments Nuclear Instruments and Methods in Physics Research A 372 3 349 351 Bibcode 1996NIMPA 372 349B doi 10 1016 0168 9002 95 01307 5 XIth International Workshop on Polarized Sources and Targets November 14 17 2005 Tokyo Japan XIIth International Workshop on Polarized Sources Targets amp Polarimetry September 10 14 2007 New York USA XIIIthInternational Workshop on Polarized Sources Targets amp Polarimetry September 7 11 2009 Ferrara Italy XIVth International Workshop on Polarized Sources Targets amp Polarimetry September 12 18 2011 St Petersburg Russia The 2013 International Workshop on Polarized Sources Targets amp Polarimetry September 9 13 2013 Charlottesville USA The 2015 International Workshop on Polarized Sources Targets amp Polarimetry September 14 18 2015 Bochum Germany D G Crabb W Meyer 1997 Solid Polarized Targets for Nuclear and Particle Physics Experiments Annual Review of Nuclear and Particle Science 47 67 109 Bibcode 1997ARNPS 47 67C doi 10 1146 annurev nucl 47 1 67 A Dael D Cacaut H Desportes R Duthil B Gallet F Kircher C Lesmond Y Pabot J Thinel 1992 A superconducting 2 5 T high accuracy solenoid and a large 0 5 T dipole magnet for the SMC target IEEE Transactions on Magnetics 28 1 560 563 Bibcode 1992ITM 28 560D doi 10 1109 20 119937 Thomas Jefferson National Accelerator Facility Hall A Helium 3 Target H Middleton G D Cates T E Chupp B Driehuys E W Hughes J R Johnson W Meyer N R Newbury T Smith A K Thompson 1993 The SLAC high density 3He target polarized by spin exchange optical plumbing PDF AIP Conference Proceedings 293 244 252 doi 10 1063 1 45130 hdl 2027 42 87509 St Goertz W Meyer G Reicherz 2002 Polarized H D and 3He Targets for Particle Physics Experiments Progress in Particle and Nuclear Physics 49 2 403 489 Bibcode 2002PrPNP 49 403G doi 10 1016 S0146 6410 02 00159 X T O Niinikoski 1971 A horizontal dilution refrigerator with very high cooling power Nuclear Instruments and Methods 97 1 95 101 Bibcode 1971NucIM 97 95N doi 10 1016 0029 554X 71 90518 0 S Isagawa S Ishimoto A Masaike K Morimoto 1978 A horizontal dilution refrigerator for polarized target Nuclear Instruments and Methods 154 2 213 218 Bibcode 1978NucIM 154 213I doi 10 1016 0029 554X 78 90401 9 T O Niinikoski 1982 Dilution refrigerator for a two litre polarized target PDF Nuclear Instruments and Methods in Physics Research 192 2 3 151 156 Bibcode 1982NucIM 192 151N doi 10 1016 0029 554X 82 90817 5 T O Niinikoski J M Rieubland 1979 Dynamic nuclear polarization in irradiated ammonia below 0 5 K Physics Letters A 72 2 141 144 Bibcode 1979PhLA 72 141N doi 10 1016 0375 9601 79 90673 X D G Crabb C B Higley A D Krisch R S Raymond T Roser J A Stewart G R Court 1990 Observation of a 96 Proton Polarization in Irradiated Ammonia Physical Review Letters 64 22 2627 2629 Bibcode 1990PhRvL 64 2627C doi 10 1103 PhysRevLett 64 2627 PMID 10041768 W Meyer 2004 Ammonia as a polarized solid target material a review Nuclear Instruments and Methods in Physics Research A 526 1 2 12 21 Bibcode 2004NIMPA 526 12M doi 10 1016 j nima 2004 03 145 J Ball 2004 Thirty years of research with lithium compounds in Saclay Nuclear Instruments and Methods in Physics Research A 526 1 2 7 11 Bibcode 2004NIMPA 526 7B doi 10 1016 j nima 2004 03 144 T R Eichhorn M Haag B van den Brandt P Hautle W Th Wenckebach 2013 High proton spin polarization with DNP using the triplet state of pentacene d14 Chemical Physics Letters 555 296 299 Bibcode 2013CPL 555 296E doi 10 1016 j cplett 2012 11 007 M S Vindinga C Laustsena I I Maximovd L V Sogaardb J H Ardenkjaer Larsene N Chr Nielsena 2013 Dynamic nuclear polarization and optimal control spatial selective 13C MRI and MRS Journal of Magnetic Resonance 227 57 61 Bibcode 2013JMagR 227 57V doi 10 1016 j jmr 2012 12 002 PMID 23298857 External links editCOMPASS experiment at CERN Retrieved from https en wikipedia org w index php title Polarized target amp oldid 1161304016, wikipedia, wiki, book, books, library,

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