XI International Workshop PST 05 Tokyo Japan November

XI International Workshop PST 05 Tokyo, Japan, November 14 -17, 2005 The Sb and HIO 3 Aligned Nuclear Targets for Investigation of Time Reversal Invariance Violation. A. G. Beda , L. D. Smirnova Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia e-mail: beda@itep. ru 1

Topics 1. Introduction. 2. Aligned targets. 2. 1. Nuclear alignment. 2. 2. Aligned nuclear targets for PCTV experiments. 3. Outlook. 2

Introduction Forward scattering amplitude for slow neutrons can be written in the following way : f(0) = A + B s I + C s p + D s p I + E s p I (p I) PVTV PCTV where s, I , p are the neutron spin , spin of the target nuclei and neutron momentum respectively. Investigation of fundamental symmetries violation (spatial parity and time invariance ) in neutron-nuclear interactions is rather perspective due to large enhancement of effects of violation in the compound resonances. 3

Real progress in this field was hampered in the first place by absence of appropriate oriented nuclear targets, by serious methodical problems ( in the case of threefold correlation) and to some extent by insufficient intensity of sources of resonance neutrons. Now the creation of the two neutron spallation sources (JSNS, Japan and SNS, USA) are in progress. Their intensity will be more than intensity of present sources by a factor 20 -30. 4

Today the japanese physicists are successful in the development of polarized nuclear target La. Al. O 3+Nd 3+ Real progress in the development of aligned nuclear target is achieved in Russia. The Sb and Hi. O 3 single crystals are grown and the construction of PTR based dilution refrigerator is developed. 5

2. Aligned nuclear targets 2. 1. The nuclear alignment Interaction of nucleus qadrupole moment Q with gradient of electric field eqzz results in splitting of the ground state over 2 I– 1 double (± mi) degenerated substates. ЕQ (mi)= e. Qqzz [ 3 mi 2 - I(I+1)] / 4 I(2 I-1) Recall that an ensemble of nuclei with spin I 1 is aligned if the parameter of alignment р2 (I) is nonzero р2 (I) = [3 m 2 – I (I+1) ] / I (2 I– 1) Here m 2 = ( mi 2 ni) / ni and ni is a population of substate mi. 6

If the spins are in equilibrium at the temperature T 0 the distribution of ni over substates is given by Boltzman law, at T= 0. 5 K and NQR ~ 100 MHz p 2 equilibr =0. 5% The high degree of nuclear alignment р2 (I) can be achieved by dynamic nuclear alignment (DNA) method (Atsarkin, Beda et al, 2000) or sometimes by brute force method. 7

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The main problem of the realization of DNA method is the selection of an appropriate compound, which has to meet the following requirements: 1. high content of nuclei of interest, 2. high quadrupole energy splitting of the nuclear sublevels (NQR frequency > 30 MHz ) 3. high energy splitting of the sublevels of the paramagnetic impurities, EPR frequency > 30 GHz 4. possibility of growing large single crystal. At the first stage, the Lu. Nb. O 4 + Cr 3+ single crystal was grown, NQR ~ 100 MHz, EPR = 9, 7 GHz 9

2. 2. Aligned nuclear targets The suitable targets for study TRI violation with the use FC correlation are the nuclei with I 1 having low lying p-wave resonances. Number of p-wave Natural resonance in the Isotope Abundance Spin range 0 -350 e. V % 115 In 96 9/2 40 121 Sb 57 5/2 17 123 Sb 43 7/2 6 127 I 100 5/2 20 10

I 2 (e. Qq 0) ni 1/2 0. 095 0. 95 334 MHz 3/2 0. 21 0. 97 643 MHz 5/2 1 1 P 2 = 0. 68 0. 016 11

A. L. Barabanov, A. G. Beda, J. Phys. G: Nucl. Part. Phys. 31 (2005) 161 -178 12

The value of the effect рт is рт = k l Factor k includes nuclear characteristics, l is the target thickness in cm. The statistical error Δ of measurements Δ = 1/ ( Io S T e –l/λ )1/2, The necessary condition for observation of the effect р. T /Δ ≥ 3 13

Sb single crystal obtained by Chokhralsky method (50 X 40 X 60 mm 3) 14

Big–sized single crystals (volume about 100 cm 3) can be grown from following compound : Sb I In Sb 2 Te 3 HIO 3 In. As Bi 0. 2 Sb 1. 8 Te 3 Li. IO 3 In. Sb Bi 0. 4 Sb 1. 6 Te 3 Tl. I-Tl. Br Ga. Sb In. Sb 15

HIO 3 Li. IO 3 16

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Impressive progress in the field of low temperature technique during the last years was achieved. The new type of the dilution refrigerator was developed: precooled by a commercial two-stage pulse-tube refrigerator (PTR). No cryoliquids are needed to operate such millikelvin cooler. Such refrigerator makes it possible to carry out the experiments at m. K temperatures with good movability, automatic cooling-down, easy handling, low running coast, stable and continuous operation, and no neutron beam loss due to the refilling liquid helium. It can also provide rather high cooling power which makes possible to cool down the samples of large mass. Now this two stage PTRs are produced in USA (Cryomech), Germany (Veri. Cold) and Japan (Janis). 18

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Outlook 1. Application of HIO 3 and Sb single crystals opens the way for study of PCTV interactions. 2. The use of pulse tube based dilution refrigerator provides possibility of nuclear alignment by brute force method. 3. The use of HIO 3 and Sb targets in the experiments at SNS or JSNS will make possible to discover TRI violation or to decrease the current limit on intensity of PCTV interactions by two orders of magnitude. 20

Thank you 21

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Two stages of experiments (3(p I)2 24