Progress of polarized HD target

  HD group LEPS RCNP

C. Morisaki

① Development of NMR measurement system

for the polarized HD target

② Development of single crystal HD target

・ contents

In the case of proton in HD, ～ 95% of polarization will be expected at 17 Tesla and 10mK.

① NMR T. Kunimatsu (RCNP) K. Fukuda (Kyoto univ.) (C. Morisaki)

How to measure ?

“ the NMR method ”

Check the NMR spectra of LH2 with use an one of the NMR system, called “single coil method”.

・ A first step of NMR

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 coilcovers the whole region

The H2 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 LH2 with single coil method

※ 　 Resonance frequency of H2 is about 17MHz at field of 0.407Tesla.

0.405 0.407 0.41magnetic field (T)

mag

nitu

de o

f sig

nal

(V)

Im partRe part

The longitudinal relaxation time Ｔ１ of NMR is related to the intensity of the signal and the transverse relaxation time Ｔ２ is related to the line width.

T1 : It is time from after stop a 90°pulse to system backs a equilibrium to vertical.

apply 90°pulse and stop

T2 : 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/T1) . t ： time

Signal depends on dP/dt = (- １ /T1) ・ exp(-t/T1) .

The shorter T1 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.

LH2 in a cell

→ The sharp peak came from LH2 . { T1:short

→ Hydrogen included in Stycast brought about the broad peak. 　　 　　 { T1: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.

・ Summary of NMR

singleLH2 →

crossedLH2 →

crossedHD

Stycast Kel-FKel-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.

② Single Crystal (SC) M. Utsuro (RCNP) T. Kuwai (Toyama univ.) T. Ohta (RCNP)

at inner of dilution refrigerator (DR)

low thermal conductivity→ ～ 10 W/K ・ m high thermal conductivity→ about ～ 103 W/K ・ m

But ・・・6m Ｋ

a few ten mK

6m Ｋ

below10mK

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

・ What is the 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 making method of SC

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

・ A first step of SC development at lab of the University of Toyama.

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.

・ Summary of single crystal

Fin