MASTER LBL-13429 fijnnr-®lfi'to~ M3 Lawrence Berkeley Laboratory UNIVERSITY OF CALIFORNIA Accelerator & Fusion Research Division Presented at the 9th Symposium on Engineering Problems of Fusion Research, Chicago, IL, October 27-30, 1981 ACDOS2: A CODE FOR NEUTRON-INDUCED ACTIVITIES AND DOSE RATES Lawrence Ruby, Gregory S. Keney, and Jean-Chkrles Lag&che October 1981 Prepared for the U.3. Department of Energy under Contract W-7405-ENG-48 draiaiiTiDK OF tins m a r is mam®,

The properties of the Mathieu equation are reviewed in order to discuss some of the applications that have appeared in recent years. Those mentioned are: vibrations in an elliptic drum, the inverted pendulum, the radio frequency quadrupole, frequency modulation, stability of a floating body, alternating gradient focusing, the Paul trap for charged particles, and the mirror trap for neutral particles.

"Comment on the Physical Interpretation of the Flux." Nuclear Science and Engineering, 109(1), p. 111

An alternative mixed beam neutral beam injector (MNBI) for fusion reactors is proposed that eliminates the conventional isotope separation system (ISS) in the fuel cycle. The principal advantage of the alternative system is a capital and operating cost savings in the fuel cycle, as the ISS employs cryogenic distillation at liquid-hydrogen temperatures to effect a separation of hydrogen isotopes and to eliminate a buildup of normal hydrogen in the recycled fuel. Possible additional advantages of the alternative method involve an improvement in overall safety and a reduction of the amount of tritium in the fuel cycle. The alternative heating system uses an electromagnetic separation in the MNBI to limit the buildup of normal hydrogen. Calculations indicate that an MNBI can be reasonably optimized in the case of an upgraded injection system for the Tokamak Fusion Test Reactor.

Production of nuclear-spin-polarized atoms by "collisional pumping" is proposed. Collisional pumping utilizes a succession of charge-transfer collisions between a fast ion or atom beam and a thick electron-spin-polarized target to polarize the beam. Calculational results are presented for 20-keV/u H or D ions or atoms incident on a polarized target. The process appears to have unique capabilities for polarizing fast H, D, T, and perhaps other nuclei, with the possibility of producing ampere currents.

Collisional pumping has been proposed as a mechanism for efficient transfer of spin from an electron-spin-polarized target to the nuclei of a fast atom or ion beam. Collisional pumping takes place in low magnetic fields, can give polarization transfer approaching 100%, and offers the potential for producing polarized beams orders of magnitude more intense than presently achieved. Recently reported calculations of electronic spin-exchange cross sections at useful ion-source energies suggest significantly greater rates of pumping than first estimated, and give cause for increased optimism about sucessful implementation. Collisional pumping is described, and beam characteristics are given for prototype polarized source parameters.

Recent measurements designed to measure neutral-beam species by nuclear reaction analysis are reported. The detection system and several experiments intended to improve resolution and reduce noise are described. Results obtained at the LBL neutral-beam engineering test facility are discussed and compared with the predictions of optical Doppler-shift spectroscopy.

Collisional pumping has been proposed as a mechanism for producing polarized ion beams more intense by orders of magnitude than those from the best existing sources. One implementation of this method employs a very thick electron-spin-polarized alkali-vapor target in a low magnetic field, and is characterized by a predicted 100% spin-transfer efficiency from the target to the beam. Target characte...

Several authors have studied the Kolmogorov equation for a fission-driven chain-reacting system, written in terms of the generating function G(x,y,z,t) where x, y, and z are dummy variables referring to the neutron, delayed neutron precursor, and detector-count populations, n, m, and c, respectively. Pal and Zolotukhin and Mogil'ner have shown that if delayed neutrons are neglected, the solution is approximately negative binomial for the neutron population. Wang and Ruby have shown that if the detector effect is neglected, the solution, including the effect of delayed neutrons, is approximately negative binomial. All of the authors assumed prompt-neutron emission not exceeding two neutrons per fission. An approximate method of separating the detector effect from the statistics of the neutron and precursor populations has been proposed by Ruby. In this weak-coupling limit, it is assumed that G(x,y,z,t) = H(x,y)I(z,t). Substitution of this assumption into the Kolmogorov equation separates the latter into two equations, one for H(x,y) and the other for I(z,t). Solution of the latter then gives a generating function, which indicates that in the weak-coupling limit, the detector counts are Poisson distributed. Ruby also showed that if the detector effect is neglected in the equation for H(x,y), i.e., the detector efficiency ismore » set to zero, then the resulting equation is identical with that considered by Wang and Ruby. The authors present here an approximate solution for H(x,y) that does not set the detector efficiency to zero.« less

Neutral-beam heating and/or fueling offers the possibility of establishing deuteron and triton spins oriented parallel to the magnetic field (or antiparallel to the field). It is believed that the polarizations can be maintained by guide fields until the particles are within the reactor. A beam suitable for this magnetic fusion-energy application would require five to six orders of magnitude increase in polarized beam intensity from the limits imposed by present technology, which is on the order of 10-100 ..mu..A. We have recently proposed that ampere-sized beams of nuclear-spin-polarized ions and atoms can be produced by multiple atomic collisions in an electron-spin-polarized medium. By analogy to optical pumping, we have called the process ''collisional pumping.'' Such pumping will occur when an ion beam passes through a thick electron-spinpolarized target in a low magnetic field. As an ion in the beam undergoes a succession of electron-capture and -loss collisions, polarization is transferred from the electron to the nucleus through the hyperfine interaction. After a sufficient number of charge-changing collisions, both the electron and nuclear polarization of the beam will be pumped to the electron polarization of the target. We have analyzed and theoretically demonstrated several examples of collisional pumping; the case thatmore » lends itself to earliest testing is that of a low-energy (0.1 - 10 keV/u) hydrogen or deuterium beam passing through a thick electron-spin-polarized alkalivapor target in a low magnetic field.« less

Major discoveries, which have transformed The Periodic System of the Elements from the arrangement suggested by Mendeleev to the current configuration, are reviewed. In particular, the contributions of H. G. J. Moseley and G. T. Seaborg are described.

The production of polarized negative ion beams by ‘‘collisional pumping’’ is described. Collisional pumping utilizes repeated charge changing collisions in a thick electron‐spin‐polarized gas or vapor target to form a polarized fast atom beam. The polarized fast atom beam is then partially converted into a polarized negative ion beam in a vapor target. Analysis is presented for a hydrogen beam passing through either a thick polarized H atom target or a thick polarized alkali target. Large polarizations and large currents may be possible.

The Chapman-Kolmogorov equation for a neutron chain-reacting system is solved in the weak-coupling steady-state limit in which the independence of the detection process can be assumed. The counter probability distribution is found to be Poissonian and the neutron probability distribution is found to be negative binomial.

LBL-10367 TRACE IDENTIFICATION OF CESIUM AND Lawrence Ruby Lawrence Berkeley Laboratory and Department of Nuclear Engineering University of California Berkeley, California 94720 Cesium and sodium in vapor form are used in two of the approaches ' to negative-ion production for neutral-beam research. Since fusion reactors are sensitive to the presence of high-Z impurities, it is important to monitor the extent to which the cesium and sodium migrate in the beam direction, or travel as part of the beam itself. Two techniques have been developed for the trace One of identification of either cesium or sodium on targets placed in vacuum. these involves neutron activation, and the other alpha-backscattering, to provide quantitative identification. Three types of targets have been employed, polyethylene which is suitable for the activation technique, beryllium which is useful for the alpha-backscatter analysis, ard glassy carbon which is usable with either technique, and therefore, for cross comparison. The neutron-activation technique makes use of the reactions n + m Cs •+ Cs (2.90h), and n + J Na - Na (15.lh). The 0.128-MeV gamma ray from 134m Cs and the 1.369-MeV gamma ray from aid of a Ge(Li) detector. Na are subsequently counted with the To make the measurements quantitative, several cesium or sodium standards are irradiated and counted along with the targets which have been exposed in vacuo. The standards are made by pipetting 0.10 ml of solution containing a known amount (several pg) of either cesium or sodium in the form of a soluable salt, onto a polyethylene target and then evaporating to dryness. Before irradiation, each target is inserted into an individual polyethylene *This work was supported by U. S. Department of Energy, Office of Fusion Energy, under contr-t No. W-7405-ENG-8.