Dale W. Heikkinen

Effects of 14-MeV Neutron Irradiation on Optical Components for Fusion Diagnostics

Various kinds of optical fibers and related optical components for fusion diagnostics were irradiated with 14-MeV neutrons from OKTAVIAN or RTNS-II. This report shows typical fusion neutron irradiation effects on them and their hardness levels to mean 14-MeV neutron fluences at which their important performance degrades 10%. Also experimental formulas for fusion neutron induced backgrounds of scintillators and a photomultiplier tube are given by fitting their pulse height distributions for 14-MeV neutrons with a summation of exponential functions. These data and formulas are useful for the estimation of lifetimes and background levels of optical fusion diagnostic systems which may be located in the 14-MeV neutron environment of a fusion reactor.

Evidence for a strongly deformed prolate shape at N = 87 from 154Eu and 152Eu(p, t) reactions

Abstract The (p, t) reaction on radioactive targets of 152,154Eu has been used to study rotational states associated with the { p 5 2 [413]; n 11 2 [505]} K=3 − configuration in the transitional odd-odd 152Eu and 150Eu nuclei. Our studies yieldcompelling evidence that this configuration in 150Eu has a prolate structure which is strongly deformed and occurs at excitation energy of 1224 keV.

On the stability of a ground-state rotational structure for the transitional nucleus 152Eu

Abstract Proton scattering from 152Eu reveals a well-behaved ground-state rotational structure. This result emphasizes the strong influence of the h 11 2 orbital in the A ≈ 150 region and is intimately connected with possible shape coexistence in 152Eu.

Operation in pulsed mode at RTNS-II

An experiment was done with a D/sup +/ ion source on a test stand, after which the pulsing system was installed on an RTNS-II neutron source to demonstrate its feasibility as an intense pulsed neutron source. The ion source MATS-II was run in the pulsed mode. A maximum current of 115 mA was obtained by arc pulsing, but with a pulse width of more than 200 msec. In the pulsed operation of RTNS-II, the beam was accelerated up to 360 keV and a maximum current of 80 mA was obtained on the rotating target. (LEW)

Effects of Fusion Neutron Irradiation on Photomultiplier Tubes

ments(1)~(3). Therefore, most reports have described irradiation experiments utilizing a g -source , an electron accelerator and a high energy charged particle accelerator to simulate the radiation encountered in space. There are few papers on high energy neutron effects on photomultiplier tubes. Irradiation experiments by a D-T neutron source are significant for fusion research, and data on fusion neutron effects and hardness of photomultiplier tubes are directly useful for design of fusion diagnostic systems. The purpose of this paper is to show fusion neutron effects on photomultiplier tubes and to determine how long they can be effectively used in the fusion neutron environments. Nine kinds of commercially available photomultiplier tubes were irradiated with 14 MeV neutrons from the RTNS-II(4)(5) at Lawrence Livermore National Laboratory. Table 1 lists models of the irradiated photomultiplier tubes and summarizes their construction. They were selected to vary in photocathode, dynode and window materials and dynode structure and to allow comparisons of neutron effects and hardness among them. In addition to the photomultiplier tubes, three kinds of glass plates (UV, fused silica and synthetic silica) were irradiated together to consider the coloration of the windows of the photomultiplier tubes. They are the same glasses as are used for the window materials of the following three photomultiplier tubes; R375 (synthetic silica), R760 (fused silica) and R1463 (UV). The nine photomultiplier tube samples, one for each model, and the three glass plates were set around the rotating target of the RTNSII and irradiated at room temperature. The glass plates were placed on the windows of the corresponding photomultiplier tubes for irradiation. The neutron fluences, measured with five Nb activation foils for each sample, were controlled by variations of the irradiation time and the distance between the samples and the rotating target. Finally, the photomultiplier tube and glass plate samples underwent five different irradiations and the total neutron fluences for the samples amounted to ~2 ~3 x 1015 n/ cm2. The irradiated samples were removed from the target room two days after every irradiation and were examined for their per* Yamada-oka , Suita-shi, Osaka 565. ** Livermore , California 94550, USA.

An anticoincidence-shielded NaI spectrometer designed to minimize neutron backgrounds

Abstract A 25 × 25 cm2 NaI gamma spectrometer with a plastiv anticoincidence shield has been constructed with particular regard to minimizing neutron-associated backgrounds. The spectrometer is used with the Lawrence Livermore Laboratory cyclograaff accelerator. The unique feature of the spectrometer is the use of thick shields of 6LiH completely surrounding both the central NaI crystal and the anticoincedence plastic. It is found that under normal conditions the count-rate limitation of the spectrometer is due to gammas in the central crystal emitted from accelerator target, and not to neutron-induced events.

Capacitance dilatometer for in situ measurement of radiation-induced dimensional changes of solids

We describe a new capacitance dilatometer for measuring radiation‐induced volume change of solids having high stability and capability of measuring a fractional length change of 10−6.