Versatile production method of thin targets supported by PVA Shimbara, Y; Fujita, Y; Hamaguchi, M ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2004, Letnik:
522, Številka:
3
Journal Article
Recenzirano
Thin self-supporting targets are indispensable in high energy-resolution studies using a magnetic spectrometer. However, nuclear targets of alkaline and alkaline-earth metal or halogen isotopes are ...not easily available. In order to produce thin target foils of these elements for the use in charge-exchange reactions, we take advantage of the fact that the stable isotopes of these elements have relatively small negative
Q values, while
12
C
and
16
O
have large negative
Q values. Therefore, even if organic compounds containing carbon and oxygen are used as supporting material, clean spectra on alkaline and alkaline-earth metal or halogen targets can be obtained up to the excitation energies of
Q-value differences. A technique to produce thin foils of the chemical compounds
Na
2
CO
3,
K
2
CO
3,
CaCO
3
and CaCl
2 was developed using polyvinylalcohol as supporting material. Foils with a total thickness of 1–
2
mg/
cm
2
were produced and used as targets in a
(
3
He,t)
reaction study at an incident energy of
420
MeV
. Owing to the small contributions of energy-loss differences of beam and reaction products in such thin targets, a very good resolution of Δ
E/
E=7×10
−5 was achieved in combination with a high-resolution magnetic spectrometer.
Interactions of 150MeV/amu 3He++ projectiles with solid gold targets have been studied at the isochronous cyclotron of the RCNP in Osaka. The 3He+ ions resulting from capture of the target electrons ...to the projectile were observed with the use of large magnetic spectrograph, Grand Raiden, set at θ=0° with respect to the beam. The yield ratio of singly to doubly ionized helium ions emerging from thin gold foils, He+/He++, has been measured as a function of the foil thickness. Extrapolating the results to zero Au target thickness permits to determine the cross section values for electron stripping from 3He+ ions, σSTRIP=1.05×10−17cm2, and for electron capture to 3He++ ions, σCAP=1.12×10−25cm2. The results obtained extend significantly the existing systematics for both processes to high (semi-relativistic) velocities. The collision strength deduced from the stripping cross sections deviates strongly from the theoretical predictions of Gillespie in absolute values as well as in the velocity dependence. It can, however, be well approximated by the simple Bohr formula for mid Z atoms. Also the capture data indicate the need to improve the theoretical approximations. A more detailed treatment of electrons captured from different shells in a high Z target is presumably needed. The astrophysical interest in the data of this kind for very light ions (hydrogen, helium) is indicated.
The proportionality between differential cross sections at vanishing linear momentum transfer and Gamow-Teller transition strength, expressed in terms of the unit cross section ({sigma}{sub GT}), was ...studied as a function of target mass number for (t,{sup 3}He) and ({sup 3}He,t) reactions at 115A MeV and 140A MeV, respectively. Existing ({sup 3}He,t) and (t,{sup 3}He) data on targets with mass number 12{<=}A{<=}120 were complemented with new and reevaluated (t,{sup 3}He) data on proton, deuteron, {sup 6}Li, and {sup 12}C targets. It was found that in spite of the small difference in beam energies between the two probes, the unit cross sections have a nearly identical and simple dependence on target mass number A, for A{>=}12: {sigma}{sub GT}=109/A{sup 0.65}. The factorization of the unit cross sections in terms of a kinematical factor, a distortion factor, and the strength of the effective spin-isospin transfer nucleus-nucleus interaction was investigated. Simple phenomenological functions depending on mass number A were extracted for the latter two. By comparison with plane and distorted-wave Born approximation calculations, it was found that the use of a short-range approximation for knock-on exchange contributions to the transition amplitude results in overestimated cross sections for reactions involving the composite ({sup 3}He,t) and (t,{sup 3}He) probes.
Absolute transition probabilities for the first 2{sup +} states in {sup 110,114}Pd were measured using the recoil distance Doppler shift technique following projectile Coulomb excitation at ...intermediate beam energy. This technique was applied for the first time to projectiles produced in a primary fragmentation reaction, which get Coulomb excited in a secondary reaction. The {sup 110}Pd data was used to check the novel experimental technique as well as the data analysis procedure, which is based on the examination of {gamma}-ray line shapes. Whereas the measured B(E2) value for {sup 110}Pd agrees very well with the literature, the value obtained for {sup 114}Pd differs considerably. The new experimental data are compared to calculations in the framework of the Interacting Boson Model. The data are also used to test the novel concept of valence proton symmetry, which allows for extrapolation of nuclear properties to very neutron-rich nuclei.
A new beam line that can accomplish both lateral and angular dispersion matching with the Grand Raiden spectrometer was designed and constructed at RCNP. A resolution of about 30 keV and a ...scattering-angle resolution of about 5 mrad were achieved in the (
3He,
t) reaction at
T
3
He
= 420 MeV (140 MeV/A) and angles of 0°–3°. This high-resolution and good angle-resolution reaction enables us to study nuclear structure and fine structure of giant resonances with unprecedented precision.
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