HD group LEPS RCNP C. Morisaki

① Development of NMR measurement system for the polarized HD target ② Development of single crystal HD target

 In the case of proton in HD, ～ 95% of polarization will be expected at 17 Tesla and 10mK. How to measure ? “ the NMR method ”

 Check the NMR spectra of LH 2 with use an one of the NMR system, called “single coil method”.

signal ∝ exp( iθ ) ・ Single coil method uses one coil takes both transmitter and receiver coil. ・ Cancellation circuit for keeping away signals which enter in Lock-in Amp at direct without entering in the coil. ・ single coil method

cylindrical sample cell (Stycact) NMR coil covers the whole region The H 2 consisted in the cell was liquefied at 17K. The magnetic field was swept from 0.405T to 0.41T. The signal frequency was fixed 17MHz.

 Spectra of LH 2 with single coil method ※ Resonance frequency of H 2 is about 17MHz at field of 0.407Tesla magnetic field (T) magnitude of signal (V) Im part Re part

The longitudinal relaxation time Ｔ １ of NMR is related to the intensity of the signal and the transverse relaxation time Ｔ ２ is related to the line width. T 1 : It is time from after stop a 90°pulse to system backs a equilibrium to vertical. apply 90°pulse and stop T 2 : It is time from after stop a 90°pulse to system backs a equilibrium to horizontal. apply 90°pulse and stop

Polarization P depends on exp(-t/T 1 ). t ： time Signal depends on dP/dt = (- １ /T 1 ) ・ exp(-t/T 1 ). The shorter T 1 is, the higher peak becomes. The polarization will be obtained by integration of the peak. At these points, We can think that 2 peaks are consisted by 2 sorts of Hydrogen-state which take a difference state respectively.

LH 2 in a cell → The sharp peak came from LH 2. { T 1 :short → Hydrogen included in Stycast brought about the broad peak. { T 1 :long empty cell (Stycast) ← background That is ・・・ Comparison between spectra of LH2 and non-LH2

 Make a new cell made of non-Hydrogen material in order to exclude the background. exam) Kel-F  Change the NMR system from single coil to crossed coil method has a high accuracy.  Calculate the polarization by integration of a peak area after excluding the background. single LH 2 → crossed LH 2 → crossed HD StycastKel-F

・ crossed coil method ・ Coils lie orthogonally each other. → There is no influence from magnetic field made by signals each other. ・ Coils are separated each other. → It is not necessary to use a cancel circuit.

at inner of dilution refrigerator (DR) low thermal conductivity → ～ 10 W/K ・ m high thermal conductivity → about ～ 10 3 W/K ・ m But ・・・ 6m Ｋ a few ten mK 6m Ｋ below 10mK

These aluminum wires will bring the background at LEPS experiments. ( Of course, there is few problem at LEPS experiments, if we take a difference between a date of HD which include the aluminum and a date of only aluminum.) high thermal conductivity without aluminum wires “ Single Crystal -HD target”

 Single Crystal is a crystal which has hexagonal close-packed structure. ・ Normal crystal ・ Single Crystal low density → low thermal conductivity high density → high thermal conductivity = HD

 Normal crystallization ① only cool down from 300K to 10mK  Single crystal ① cool down to around 10K which is temperature that the HD starts crystallization ② make a difference of temperature in between a bottom of the cell and a top of the cell to use heaters, cool down at a fair low speed, insert the HD in the cell slowly, crystallize the HD from the bottom of the cell

 A conductivity measurement on SC-HD was undertaken with LHe cryostat.

 After crystallization, the conductivity measurement was carried out. result This is the world first report on thermal conductivity of the single crystal HD. Heat flow // z-axis

 The improved measurement will be performed soon. The conductivity will be further enhanced with ( ⅰ ) higher HD purity (>99.9%) prepare with a distillation apparatus to reduce the impurity contribution; by about 100 times, and ( ⅱ ) heat flow perpendicular to the z-axis of the single crystal; by about 50 times.

(250 mK) (250 mK) ? γ p γ p K－K－ unobservableobservable ・ a new one K＋K＋ K＋K＋ K－K－ dipole

 Make a sample nose made of SUS, thin layers made of cupper  Play a cooling test of sample nose to 250mK at RCNP

Fin