Transcript 0度(p,p`)による 28SiのM1励起に関する研究

０度(p,p’)による
28SiのM1励起に関する研究
阪大RCNP 松原礼明
25.Mar.2005 物理学会
Collaborators
阪大RCNP
民井淳、畑中吉治、酒見泰寛、伊藤正俊、新原佳弘、
清水陽平、藤田訓裕、中西康介、爲重雄司、橋本尚信
阪大理
藤田佳孝、足立竜也
Univ. of Witwatersrand
J. Carter
東大CNS
川畑貴裕
京大理
坂口治隆、與曽井優、銭廣十三
iThemba LABs
F.D. Smit、藤田浩彦
Gent Univ.
L.A. Popescu
25.Mar.2005 物理学会
Introduction
• The configuration mixing is a main theme for
the understanding of the nuclear structure.
• The M1 excitations from 0+ T=0 nucleus are
one of the good probes.
• Light nucleus is easier to be calculated, e. g.
sd-shell one.
24Mg, 28Si, 32S
25.Mar.2005 物理学会
Quenching problems
• Less strength is observed than predicted with sum rule.
GT sum rule :
 0 | [Y  , Y  ] | 0  3 ( N  Z )
60 → 90% of the strength is observed.
T.Wakasa et al., PRC55(1997)2909 (p,n) reaction
How about M1 strengths?  , 
Common with GT
Quenching is observed in T=0,1 M1 strengths in 28Si.
N. Anantaraman et al.,PRL52(1984)1409
Almost no quenching is observed in 24,26Mg, 28Si, 32S.
G.M. Crawley et al.,RPC39(1989)311
Improvement of the data quality is required.
25.Mar.2005 物理学会
Experimental Setup (@RCNP WS course)
Under focus mode
As a beam spot monitor
in the vertical direction
Q1 F.C.
Intensity : 3 ~ 8 nA
Target : natSi (1.9 mg/cm2)
25.Mar.2005 物理学会
Procedure of the beam tuning
• Achromatic transport mode
~40keV (FWHM) : Au(p,p0) at 8°
• Halo free beam tuning at 0°
(achromatic mode)
• Dispersion matching
(faint beam method)
~3mm (FWHM) on the target : beam spot size
It took about 2 days for beam tuning.
25.Mar.2005 物理学会
Sieve slit calibrations
Sieve slit data :
58Ni(p,p ) reaction at 16°
0
Horizontal:
Δθ= 0.15 deg
Vertical :
Δφ= 0.5 deg at Ex = 6 MeV.
0.8 deg at Ex = 20 MeV.
ΔΘ = 0.5 ~ 0.8 [deg]
25.Mar.2005 物理学会
Background subtraction
25.Mar.2005 物理学会
A high quality spectrum
25.Mar.2005 物理学会
G.M. Crawley et al, PRC39(1989)311, at Orsay
2000
1500
500
Present data
25.Mar.2005 物理学会
The Differential Cross Section
OXBASH parameter from A. Willis et al., PRC 43(1991)5
25.Mar.2005 物理学会
Summary
•
experiments at forward angles were carried
out at RCNP WS course.
natSi(p,p’)
• High quality beams were obtained.
• For the first time we succeeded in
under-focus mode (scattering angle : 0.5~0.8 deg)
dispersion matching (excitation energy : ~20 keV)
for the (p,p’) measurement at 0 degree.
• Background was subtracted reasonably.
• The cross sections of 1+ of both IS and IV type were
compared with DWBA calculations.
25.Mar.2005 物理学会
Future
• Jπ assignments of each peak
• Extraction of M1 strengths and their
distributions
• Next beam time
– Angular distributions
– Data for further calibrations
25.Mar.2005 物理学会