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Nuclear Instruments and Methods in Physics Research A 526 (2004) 153–156 Frozen spin solid targets developed at JINR Dubna Yuri Usov JINR, Dubna 141980, Russia Abstract Experience with polarized targets and the achievement of very low temperatures at the Laboratory of Nuclear Problems (JINR, Dubna) and at other places have triggered the idea of using a radically new technique based on dissolving 3 He in 4 He to create a frozen spin polarized target. The short history of the development of such proton and deuteron targets at the LNP is given. Diols with the complex Cr(V) are used as target materials. A characteristic feature of these targets is the long relaxation time (E1000 h) in magnetic fields of about 0:5T: Lately, the Saclay–Argonne frozen spin polarized proton target used initially in the E704 experiment at FERMILAB has been upgraded by adding the missing parts. A first physics experiment has been carried out. r 2004 Elsevier B.V. All rights reserved. PACS: 29.25.Pj Keywords: Polarized targets 1. Frozen spin polarized targets Experience with Dynamically Polarized Targets and achieving Very Low Stationary Temperatures in 1966 at JINR [1] by Neganov, Borisov and Liburg and another group [2] gave rise to the IDEA of using a radically new cooling technique based on dissolving 3 He in 4 He; to create a frozen spin polarized target. In fact, three facilities of this type had been developed which are used until now in experiments at the beams of IHEP-Protvino, PNPI-Gatchina and Charles University-Prague. The short history of the development of such proton and deuteron targets at the JINR is given. The principle of operation of a frozen spin target is based on a long nuclear spin relaxation time at low temperatures (E50 mK) and moderate magnetic fields (E0:3 T). After the polarization build-up with the dynamic nuclear polarization process, the microwave power is turned off and the polarization is ‘‘frozen in’’. Then the magnetic field is lowered to about 0:3T; so the spin relaxation time can be many days at about 50 mK: In 1975 at the Laboratory of Nuclear Problems of JINR the experiments were begun at the Phasotron of LNP with a measurement of a polarization parameter in the elastic pp-scattering using a newly made frozen spin proton target PT [3]. This target is working at Gatchina until now. The next target with 20 cm length and 60 cm 3 in volume [4] has been used for experiments with 40 GeV p mesons and 70 GeV protons at the accelerator of the Institute of High Energy Physics in Protvino since 1978. Lot of articles (over 40) were published since 1976 using these two targets. ARTICLE IN PRESS E-mail address: [email protected] (Y. Usov). 0168-9002/$ - see front matter r 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2004.03.167

Frozen spin solid targets developed at JINR Dubna

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Page 1: Frozen spin solid targets developed at JINR Dubna

ARTICLE IN PRESS

Nuclear Instruments and Methods in Physics Research A 526 (2004) 153–156

E-mail a

0168-9002/$

doi:10.1016

Frozen spin solid targets developed at JINR Dubna

Yuri Usov

JINR, Dubna 141980, Russia

Abstract

Experience with polarized targets and the achievement of very low temperatures at the Laboratory of Nuclear

Problems (JINR, Dubna) and at other places have triggered the idea of using a radically new technique based on

dissolving 3He in 4He to create a frozen spin polarized target. The short history of the development of such proton and

deuteron targets at the LNP is given. Diols with the complex Cr(V) are used as target materials. A characteristic feature

of these targets is the long relaxation time (E1000 h) in magnetic fields of about 0:5 T: Lately, the Saclay–Argonnefrozen spin polarized proton target used initially in the E704 experiment at FERMILAB has been upgraded by adding

the missing parts. A first physics experiment has been carried out.

r 2004 Elsevier B.V. All rights reserved.

PACS: 29.25.Pj

Keywords: Polarized targets

1. Frozen spin polarized targets

Experience with Dynamically Polarized Targetsand achieving Very Low Stationary Temperaturesin 1966 at JINR [1] by Neganov, Borisov andLiburg and another group [2] gave rise to theIDEA of using a radically new cooling techniquebased on dissolving 3He in 4He; to create a frozenspin polarized target. In fact, three facilities of thistype had been developed which are used until nowin experiments at the beams of IHEP-Protvino,PNPI-Gatchina and Charles University-Prague.The short history of the development of suchproton and deuteron targets at the JINR is given.The principle of operation of a frozen spin

target is based on a long nuclear spin relaxationtime at low temperatures (E50 mK) and moderate

ddress: [email protected] (Y. Usov).

- see front matter r 2004 Elsevier B.V. All rights reserve

/j.nima.2004.03.167

magnetic fields (E0:3 T). After the polarizationbuild-up with the dynamic nuclear polarizationprocess, the microwave power is turned off and thepolarization is ‘‘frozen in’’. Then the magnetic fieldis lowered to about 0:3 T; so the spin relaxationtime can be many days at about 50 mK:In 1975 at the Laboratory of Nuclear Problems

of JINR the experiments were begun at thePhasotron of LNP with a measurement of apolarization parameter in the elastic pp-scatteringusing a newly made frozen spin proton targetPT [3]. This target is working at Gatchina untilnow.The next target with 20 cm length and 60 cm3 in

volume [4] has been used for experiments with40 GeV p� mesons and 70 GeV protons at theaccelerator of the Institute of High Energy Physicsin Protvino since 1978. Lot of articles (over 40)were published since 1976 using these two targets.

d.

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GATCHINA

DUBNA

PROTVINO

PRAGUE

IHEP

Charles University

PINP

2230 km

910 km

270 km

Fig. 1. The map of JINR’s frozen polarized target activities.

Y. Usov / Nuclear Instruments and Methods in Physics Research A 526 (2004) 153–156154

In 1988 the second frozen target was upgraded tothe deuteron mode [5].In 1994 we put into operation the new target

20 cm3 in volume, intended for polarizationparameters studies in np-scattering using 15 MeVpolarized neutron beam produced by the Van deGraaff accelerator of the Charles University,Prague. This target is a complex which includes astationary cryostat with a dilution refrigerator, amovable magnetic system providing a ‘‘warm’’field and consisting of a superconducting solenoidand a superconducting dipole magnet with a largeaperture, and electronic equipment for providing adynamic polarization and NMR-signal detection[6]. The further development of this target isunder preparation for deuteron polarization fornext experiments [7]. The purpose of this projectis to study three-nucleon interactions using a14–16 MeV polarized neutron beam in conjunc-tion with a polarized deuteron target.The latest development is the reconstruction of

the Saclay–Argonne frozen spin proton polarizedtarget [8] which was built for and used initially inexperiments at Fermilab. A new quality was givento the target during this reconstruction—a trans-portability from one experimental area to another.All the major parts of the target assembly disposedclosely to the beam line are mounted on twoseparate decks, which can be moved as blocks in

Table 1

Parameters of the JINR frozen polarized targets

Year of Volume Material Magnetic

the first (cm3) field (T) dynami

publ. frozen mode

1976 15 C3H6ðOHÞ2 2.69/2.69

1,2-propanediol

with Cr(V)

1980 60 C3H6ðOHÞ2 2.06/0.45

with Cr(V)

1985 60 (CD2ODÞ2 2.06/0.45

deuterated

ethanediol

with Cr(V)

1994 20 C3H6ðOHÞ2 2.7/0.37

with Cr(V)

1995 140 C3H6ðOHÞ2 2.7/2.7

with Cr(V)

and out of the beam, and also between variousaccelerators. This is the movable polarized target(MPT) concept [9]. The larger of the two deckscontains the dilution refrigerator, a 30 l serviceDewar, a 1000 l supply helium Dewar and apumping system. The pumping system consistingof three Roots pumps (RP-3600, WS-1000, WS-250) is mounted on a compact stage and placedonto the deck using pneumatic dampers forvibration isolation.All the frozen polarized targets developed at

JINR are characterized by relatively low basetemperatures. This feature is a result of long-time

Accelerator Maximum Tmin

c/ (place) polarization (%) (mK)

Dubna, Gatchina P7 ¼ 9872 36

(in use)

Protvino P7 ¼ 8773 20

(in use)

Protvino P7 ¼ 3773

(in use)

Prague Pþ ¼ 9373 20

(in use) P� ¼ 9872

Dubna Pþ ¼ 8473 50

(in use) P� ¼ 9173

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Y. Usov / Nuclear Instruments and Methods in Physics Research A 526 (2004) 153–156 155

traditions in the field of ultralow temperaturesobtained by the 3He–4He dissolving method, aswell as a consequence of using in these targetscryostats with liquid nitrogen precooling havinglarge volumes of 1 and 4 K baths. Such cryostatsdiffer significantly from Roubeau cryostats wherea cooling is reached by adjusting the flows of liquid4He: At low beam intensities these refrigeratorspermit to have lower target temperatures andcorrespondingly longer relaxation times.In Table 1 the main parameters of the frozen

polarized targets of JINR are listed.

Fig. 2. The ‘‘first’’ frozen polarized target at the beam area,

Dubna, 1975.

Fig. 3. The low-temperature part of the dilution refrigerator.

Dubna, 1975.

Fig. 4. The second frozen polarized target before transporta-

tion to Protvino. Dubna, 1978.

2. Plans

* Availability of the target (‘‘MPT’’) at JINRwith transversal polarization of protons ordeuterons gives new unique possibilities for anew generation of experiments (‘‘MRS’’, ‘‘Del-ta-Sigma’’ and ‘‘BES’’) which can be carried outat energies above 1 GeV:

* New possibility of high deuteron polarization(DNP with trityl-radicals) for the Project ‘‘NN-Interaction’’ at Charles University, Prague.(Figs. 1–4).

References

[1] B.S. Neganov, N.S. Borisov, M.Yu. Liburg, JETP 50 (1966)

1445.

[2] H.E. Hall, P.J. Ford, E. Tompson, Cryogenic 6 (1966)

80.

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Y. Usov / Nuclear Instruments and Methods in Physics Research A 526 (2004) 153–156156

[3] N.S. Borisov, et al., JINR Preprints 13-10253, 10-10257,

1976;

N.S. Borisov, et al., Prib. Techn. Exp. 2 (1978) 32.

[4] N.S. Borisov, et al., JINR Communication 1-80-98, 1980.

[5] N.S. Borisov, et al., J. Phys. E: Sci. Instrum. 21 (1988) 1179.

[6] N.S. Borisov, et al., Nucl. Instr. and Meth. A 345 (1994) 421.

[7] N.S. Borisov, et al., Particles Nuclei. Lett. 4 (2002) 113.

[8] P. Chaumette, et al., Proceedings of the Eighth Inter-

national Symposium on High Energy Spin Physics, Min-

neapolis, Minnesota, 1988.

[9] N.A. Bazhanov, et al., Nucl. Instr. and Meth. A 372 (1996)

349.