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Investigation of Time Reversal Invariance Violation with Aligned Nuclear Targets

Explore the enhancement of fundamental symmetries violation effects using aligned nuclear targets, advancements in nuclear alignment techniques, and the development of novel dilution refrigerators for low-temperature experiments.

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Investigation of Time Reversal Invariance Violation with Aligned Nuclear Targets

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  1. XI International Workshop PST05 Tokyo, Japan, November 14-17, 2005 The Sb and HIO3 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

  2. Topics 1. Introduction. 2. Aligned targets. 2.1. Nuclear alignment. 2.2. Aligned nuclear targets for PCTV experiments. 3. Outlook.

  3. 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) PV PVTVPCTV 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.

  4. 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.

  5. Today the japanese physicists are successful in the development of polarized nuclear target LaAlO3+Nd3+ Real progress in the development of aligned nuclear target is achieved in Russia. The Sb and HiO3 single crystals are grown and the construction of PTR based dilution refrigerator is developed.

  6. 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 2I–1 double (± mi) degenerated substates . ЕQ (mi)= eQqzz [ 3mi2 - I(I+1)] / 4I(2I-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 m2 – I (I+1) ] / I (2I–1) Here  m2 = (  mi2 ni) / ni and ni is a population of substate mi .

  7. If the spins are in equilibrium at the temperature T0 the distribution of ni over substates is given by Boltzman law, at T= 0.5 K and NQR ~ 100 MHz p2equilibr =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.

  8. The main problem of the realization of DNA method is the selection of an appropriate compound, which has to meet the following requirements: • high content of nuclei of interest,  • high quadrupole energy splitting of the nuclear sublevels (NQR frequency > 30 MHz ) • high energy splitting of the sublevels of the paramagnetic impurities, EPR frequency > 30 GHz • possibility of growing large single crystal. • At the first stage, the LuNbO4 + Cr3+ 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 eV % 115In 96 9/2 40 121Sb 57 5/2 17 123Sb43 7/2 6 127I 100 5/2 20

  10. I2 (eQq0) ni 1/2 0.0950.95 334 MHz 3/2 0.210.97   643 MHz 5/2 11 P2 = 0.680.016

  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 рT /Δ ≥ 3

  13. Sb single crystal obtained by Chokhralsky method (50 X 40 X 60 mm3)

  14. Big–sized single crystals (volume about 100 cm3) can be grown from following compound : Sb I In Sb2Te3 HIO3 InAs Bi0.2Sb1.8Te3LiIO3 InSb Bi0.4Sb1.6Te3 TlI-TlBr GaSb InSb

  15. HIO3 LiIO3

  16. 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 mK 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 (VeriCold) and Japan (Janis).

  17. Outlook • Application of HIO3 and Sbsingle crystals opens the way for study of PCTV interactions. • The use of pulse tube based dilution refrigerator provides possibility of nuclear alignment by brute force method. • The use of HIO3 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.

  18. Thank you

  19. Two stages of experiments (3(p I)2

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