AN EXPERIMENTAL SYSTEM FOR THE STUDY OF THERMAL PROPERTIES OF SPIN POLARIZED PARTICLES

HAL Id: jpa-00220164

https://hal.archives-ouvertes.fr/jpa-00220164

Submitted on 1 Jan 1980

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

AN EXPERIMENTAL SYSTEM FOR THE STUDY OF THERMAL PROPERTIES OF SPIN POLARIZED

PARTICLES

E. Fortson, C. Platt, O. Vilches

To cite this version:

E. Fortson, C. Platt, O. Vilches. AN EXPERIMENTAL SYSTEM FOR THE STUDY OF THERMAL

PROPERTIES OF SPIN POLARIZED PARTICLES. Journal de Physique Colloques, 1980, 41 (C7),

pp.C7-163-C7-164. �10.1051/jphyscol:1980727�. �jpa-00220164�

JOURNAL DE PHYSIQUE CoZZoque C7, supple'ment au n o 7 , Tome 41, juiZZet 1980, page C7-16;

E. N. Fortson, C.E. P l a t t and O.E. V i l c h e s

Department o f Physics, ~ n i v e r s i t y o f Washington, S e a t t Ze, Wa 9811 7 , USA.

Resume.- On d e c r i t l e d i s p o s i t i f experimental d e s t i n e ti l a mesure de l a c o n d u c t i v i t e thermique de 1 'hydrogene atomique p o l a r i s e e t de l a capaci t 6 c a l o r i f i q u e de 3 ~ e adsorbe p a r t i e l l e m e n t p o l a r i s @ . On donne une e s t i m a t i o n de c e r t a i n s des parametres de l ' e x p e r i e n c e .

Abstract.- The experimental system being prepared t o measure the thermal c o n d u c t i v i t y o f s p i n p o l a r - i z e d atomic hydrogen and t h e heat c a p a c i t y of adsorbed, p a r t i a l l y s p i n ~ o l a r i z e d 3 ~ e i s described.

Estimates f o r some o f t h e experimental parameters are given.

We have constructed an apparatus f o r the study o f thermal p r o p e r t i e s o f s p i n p o l a r i z e d p a r t i c l e s . The i n s t a l l a t i o n c o n s i s t s o f a c r y o s t a t w i t h a 7 . 7 T

s o l e n o i d and a simple d i l u t i o n r e f r i g e r a t o r ( a l - though a l l t e s t i n g so f a r has been done w i t h a 3 ~ e r e f ri g e r a t o r ) . The apparatus has a room tempera-

H+ THERMAL CONDUCTIVITY

, EXPERIMENT

MAGNETIZED NEEDLE

DILUTION REFRIGERATOR

ADSORBED 3 ~ e ( 4 )

EXPERIMENT

--

F i g . 1. Schematic o f experimental s e t up

described i n t e x t . An e x t e r n a l s o l e n o i d provides a

B 2

t u r e rf discharge atomic hydroaen source and t h e c a p a b i l i t y f o r adsorbing a v a r i e t y o f aases a t low temperature i n t o separate experimental regions.

We a r e c u r r e n t l y workinq on two experiments, one t o measure t h e thermal c o n d u c t i v i t y o f gaseous s p i n p o l a r i z e d hydrogen, and another one t o measure t h e heat c a p a c i t y o f p a r t i a l l y s p i n p o l a r i z e d He 3

adsorbed on G r a f o i l . A schematic o f the experimen- t a l setuo i s shown i n F i o . 1.

The thermal c o n d u c t i v i t y experiment i s a t present a s i m p l i f i e d v e r s i o n o f t h e experiments performed by Fokkens e t a l . 111 t o measure the t h e r - mal c o n d u c t i v i t y o f gaseous 3 ~ e , 4 ~ e and t h e i r mix- t u r e s . R e l a t i v e l y small thermal c o n d u c t i v i t i e s can be measured, b u t even more important, d e n s i t i e s o f o n l y 1014 t o 1016 atoms/cm a r s needed t o o b t a i n 3

meaningful data. The magnetic needle shown i n F i g . 1 i s a s p e c i a l f e a t u r e t h a t can be i n t r o d u c e d t o produce a l o c a l enhancement o f about 1 T i n t h e magnetic f i e l d between the o l a t e s and thus increas2 t h e d e n s i t y o f H+ i n a very small r e g i o n 121.

For the second experiment, a small adsorption heat c a p a c i t y c e l l i s attached t o t h e r e f r i g e r a t o r m i x i n g chamber. The heat c a p a c i t y o f unool a r i zed

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980727

JOURNAL DE P H Y S I Q U E

3 ~ e adsorbed on G r a f o i l has been measured i n t h e p a s t /3/. For T > 0.2K and low d e n s i t i e s t h e ad- sorbed He behaves l i k e an i n t e r a c t i n g two dimen- 3

s i o n a l Fermi gas. Deviations from i d e a l quantum behavior have been l a r g e l y accounted f o r by i n - c l u d i n g t h e e f f e c t o f two body i n t e r a c t i o n s i n t o a second v i r i a l c o r r e c t i o n t o t h e heat c a p a c i t y /4/. The e f f e c t o f t o t a l n u c l e a r s p i n p o l a r i z a - t i o n on t h e t h r e e dimensional second v i r i a l co- e f f i c i e n t has been c a l c u l a t e d by L h u i l l i e r and Laloe /5/. Above 0.2 K and f o r t h e maximum magnetic f i e l d a v a i l a b l e t o us, t h e n u c l e a r p o l a r i z a t i o n i s small, b u t i t s e f f e c t on t h e heat capacity should be measurable. We have c a l c u l a t e d t h a t a t 0.2K and B = 7 T t h e change i n the v i r i a l c o r r e c t i o n i s 1 %

.

*

Foundation, U.S.A., g r a n t DMR 77-27528 A1 1. Fokkens, K., Vermeer, W., Taconis, K.W.,

de Bruyn Ouboter, R. Physica 30 (1964) 2153.

2. Walraven, J.T.M., S i l v e r a , I . F . Phys. Rev.

L e t t . 28 (1972) 789.

3. H i c k e r n e l l , D.C., McLean, E.O., Vilches, O.E.

Phys. Rev. L e t t . 28 (1972) 789.

4. Siddon, R.L., Schick, M. Phys. Rev. A9 (1974) 907.

5. L h u i l l i e r , C., Laloe, F. J. Physique. 40 (1979) 239.