hd group leps rcnp c. morisaki. ① development of nmr measurement system for the polarized hd...
TRANSCRIPT
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 0.41
magnetic field (T)
mag
nit
ud
e 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