Prompt gamma radiation from fission fragments due to the Strutinsky-Denisov polarisation

The hard electric dipole radiation from fission fragments of ²³⁵U by thermal neutrons is predicted. The radiation arises due to the Strutinsky-Denisov-induced polarisation mechanism. The probability of the radiation is at the level of 0.0025 per fission, which is in agreement with experiment. The angular distribution exhibits left-right asymmetry with respect to the plane perpendicular to the neutron polarisation axis. That means that the emission of gamma quanta at the given angle depends on the neutron polarisation. The asymmetry is at the level of 10^-3. This effect is similar to that observed earlier for gamma quanta in binary and alphas in ternary fission. The study of this effect will give information about dissipation of the collective energy of the surface vibration in fragments with large amplitude, and gives a picture of the process of snapping back the nuclear surface.     

A method for calculating specific activity of fission products

An algorithm is described for determination of specific activity of any member of a linear decay chain. The algorithm permits calculation of the activity of fission products for all three possible accumulation modes: 1) coexistence, i.e., irradiation time in a reactor; 2) delay after preceding coexistence; 3) delay after instantaneous fission. In comparison with previous studies in this area the proposed method is more suitable for use with computers, both from the point of view of calculating input parameters and accuracy, as well as in convenience of programming.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 32–34, September, 1972.     

Spectral and total intensity of radiation of relativistic electrons and positrons with planar channeling

The spectral and total intensity of radiation of relativistic electrons and positrons is considered within the framework of a Langevin approach to the theory of transit of fast charged particles across a crystal. It is shown that one of the terms of the total intensity of radiation increases exponentially rapidly along those segments of the path that are in regions in which the potential of the planar channel of the crystal has negative Gaussian curvature. Surgut State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 42–44, September, 1997.     

Noise sensitivity to gamma radiation in Si-jfet devices

The result of noise measurements for a Charge Sensitive Preamplifier based on Si-Field Effect Transistor exposed to a total Gamma ray dose of 30 v Mrad have been reported. The radiation effect on the DC parameters of single transistors was also tested. Our study has shown that, there are no changes on the DC parameters. Meanwhile the noise level, which was evaluated by the total equivalent noise charge, was clearly increased. The results of noise measurements were analyzed and compared with theoretical predictions. The temperature and time-dependent effects on the noise had also been reported after irradiation. All measurements were performed for biased and unbiased irradiated transistors.     

Total beta-decay energies of heavy fission products

TheQ _β-value of^144,145Ba,^144,145,147La,^145,147,148Ce and¹⁴⁸Pr has been measured using mass-separated sources produced at the on-line mass separator LOHENGRIN. The experimental values are compared with mass formula predictions.     

静态随机存储器总剂量辐射损伤的在线与离线测试方法

以静态随机存储器为研究对象,对其在线和离线测试下的总剂量辐射损伤规律进行了研究,探寻了两种测试条件下总剂量损伤的差异并对造成差异的物理机制进行了分析和讨论,研究结果表明:由于静态随机存储器存在多种总剂量失效模式,相对于在线测试只能覆盖存储单元固定错误的一种失效模式,离线测试可覆盖多种功能失效模式;由于信号完整性对测试频率的限制,使得在线测试得到的动态功耗电流值要明显小于离线测试得到的动态功耗电流值;由于"印记效应"的存在,在线测试静态功耗电流小于离线测试中器件存储与辐照相反数据时的静态功耗电流值;在线无法测量的一些电参数,有可能先于在线可测参数而失效,这些研究结果对于静态随机存储器在星用辐射环境下的总剂量辐射损伤规律的研究和实验评估具有重要意义。     

β-decay phenomenology of nuclear fission products

Two data sets representing the two principal experimental techniques used to study the β-decay of short-lived fission fragments are analyzed. The average endpoint and electron energies for nuclei with similar Q-values are the same within statistical accuracy in the two sets. However, the spread of the endpoints is considerably larger in the data set based on integral γ-energies (ANR set) compared with the set based on standard γ-spectroscopy (ENDF set). The averaged β-strength function for the ANR set follows a “universal” trend, decreasing monotonically and rapidly with increasing β-endpoint energy. On the other hand, the β-strength function in the ENDF set is less steep, and at higher excitation energy it is considerably smaller than in the ANR set. These differences imply a systematic bias in one of these two data sets.     

Contribution of prompt muon production to total muon fluxes

Summary The flux of prompt cosmic-ray muons coming from charmed particles which are produced in both nondiffractive and diffractive processes of primary-air collisions is computed. Its maximum contribution is estimated by stressing the diffractive character of produced charmed particles. We compare the observed results on angular distributions of muon intensities at a given depth with the calculated results. There is no clear evidence for prompt muons. In a more quantitative analysis, χ² tests with regard to the expected form of the muon spectrum are performed. The expectation is based on a formula of Thompson and Walley for muons coming from pion and kaon decay which shows a sec θ enhancement plus a part of prompt muons. From these quantitative analysis, it is concluded that prompt muons may contribute to the total flux in the energy range between several TeV and several hundreds of TeV but are not beyond the maximum prediction.

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Riassunto Si calcola il flusso di muoni pronti dei raggi cosmici che derivano da particelle cariche che sono prodotte in processi sia diffrattivi che non diffrattivi di collisioni primariearia. Si stima il suo contributo massimo sottolineando il carattere diffrattivo delle particelle con charm prodotte. Si confrontano i risultati osservati sulle distribuzioni angolari delle intensità muoni a una data profondità con i risultati calcolati. Non c'è una chiara evidenza per i muoni pronti. In un'analisi piú qualititativa si calcolano test χ² con riferimento alla forma prevista dello spettro muonico. La previsione è basata su una formula di Thompson e Walley per muoni che derivano dal decadimento di pioni e kaoni che mostra un incremento di sec θ piú una parte di muoni pronti. Da questa analisi quantitativa si conclude che i muoni pronti possono contribuire al flusso totale nell'intervallo di energia da alcuni TeV a parecchie centinaia di TeV ma non sono al di sotto della previsione massima.

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Резюме Вычисляется поток быстрых мюонов космических лучей, происходящих от очарованных частиц, которые были образованы в недифракционных и дифракционных процессах первичных соударений. Оценивается максимальная величина вклада быстрых мюонов, отмечая дифракционный характер образованных очарованных частиц. Мы сравниваем наблюденные результаты для угловых распределений мюонных интенсивностей на данной глубине с результатами вычислений. Не обнаружено явного подтверждения для быстрых мюонов. Проводится количественный анализ, χ² проверка ожидаемой формы мюонного спектра. Ожидаемая величина определяется из формулы Томпсона и Валлея для мюонов, возникающих из распадов пионов и каонов, которая обнаруживает sec θ возрастание плюс вклад от быстрых мюонов. На основании этого количественного анализа делается вывод, что быстрые мюоны могут давать вклад в полый поток в области энергий от нескольких ТэВ до нескольких сотен ТэВ.

     

Probing fission time scales with neutrons and GDR gamma rays

The time scales for nuclear fission have been explored using both pre-and postfission neutrons and GDR gamma rays. Four systems were investigated: 133-MeV ¹⁶O + ¹⁷⁶Yb and ²⁰⁸Pb and 104-MeV ⁴He + ¹⁸⁸Os and ²⁰⁹Bi. Fission fragments were measured in coincidence with PPACs. The neutrons were detected using eight detectors from the DEMON array, while gamma rays were measured using the US BaF2 array. The pre-and postfission gamma rays were determined using moving source fits parallel and perpendicular to the fission fragment emission directions. The time scales for fission for the neutrons were determined using the neutron clock technique. The gamma-ray data were fitted using a statistical model calculation based on the code CASCADE. The results of the fits from both data types were used to extract nuclear friction coefficients, γ, and fission time scales. The γ values ranged from 7 to 20, while the fission times were (31–105)×10^?21 s.     

Correlation between fractional independent yields and neutron-to-proton ratio of fission products in low energy fission

Fractional independent yields of fission products in the thermal neutron-induced fission of²³³U,²³⁵U,²³⁹Pu,²⁴¹Pu and in the spontaneous fission of²⁵²Cf have been correlated with the neutron-to-proton ratio of the fission products. The yields of the products from a fissioning system, when plotted as a function of neutron-to-proton (N/Z) ratio of fission preducts, fall on two Gaussian distribution corresponding to light and heavy fission products. The centroids of the distribution or the most probable value of neutron-to-proton ratio is found to be very close to theN/Z of the fissioning nucleus. From the most probable value ofN/Z the various parameters of charge distribution e.g. most probable massA _p, most probable chargeZ _p, the mass dispersionσ _Aand the charge dispersionσ _Zhave been obtained and are in good agreement with the experimental values ofA _pandZ _p.     

Giant vibration of fission fragments and concomitant electromagnetic radiation

Giant shape vibrations of fission fragments are described in a simple model which is based on nuclear transport theory. The friction and inertial parameters are calculated within the linear response and cranking theory, respectively. The initial conditions are chosen in the scission region following the conventional picture of the fission process at low energy. The emission of electromagnetic radiation by the form vibration is treated classically.Dedicated to Prof. Dr. H.J. Mang on the occasion of his 60th birthday     

Analysis and testing of total ionizing dose effect on several commercial optical transceivers via gamma-ray radiation

In our Letter, we selected several commercial optical transceivers, which consist of single-channel transceiver modules, parallel transmitting and receiving modules, and Ethernet passive optical network(EPON) optical line terminal(OLT) and optical network unit(ONU) modules, to do the total ionizing dose(TID) testing via the gamma-ray radiation method. The changing of current and receiver sensitivity of optical transceivers is discussed and analyzed. Based on the TID testing exposed to a TID of 50 krad(Si) at a dose rate of about 0.1 rad(Si)/s,the performance of single-channel transceivers and parallel receiving modules has not changed after 50 krad(Si)exposure, the parallel transmitting and EPON ONU modules have not worked after 40 krad(Si) and 47 krad(Si)exposure, the EPON OLT module has bit error in the process of irradiation, and it can work well after annealing;the reason for the error of OLT is analyzed. Finally, based on the theoretical analysis and testing results, this Letter provides several design suggestions to improve the reliability for optical transceivers, which can be referenced by satellite system designation for various space missions.     

Identification of gamma transitions from He and Be ternary fission fragments

He and Be ternary fission processes of ²⁵²Cf have been studied in two experiments with the Gammasphere detector array with light charged particle detectors surrounding the source. From α-γ double gated spectra, neutron multiplicity distributions were determined for related α ternary fission pairs. In going from binary to α ternary SF for approximately the same mass splittings (A ≈ 104–146) the average neutron multiplicity decreases about 0.7 AMU. In the first light charged particle (LCP) γ-γ experiment, the ¹⁰Be spectrum was cutoff below 27 MeV and in the recent experiment, below 18 MeV. For high energy (E > 27 MeV) ¹⁰Be ternary fission, the data indicate that the largest yields go via the cold process (zero neutron evaporation). In the recent experiment with E cutoff of 18 MeV, the ¹⁰Be ternary SF was observed for zero to 4n emissions. It seems that in some cases like ¹³⁶Te, the On channel is the strongest and in the other cases like ¹⁰⁰Zr the 1n or 2n channel dominates. Clearly, there is a shift to lower average number of neutrons emitted for ¹⁰Be compared to α ternary SF. The ¹⁰⁴Zr and ¹³⁶Te cases where zero neutron emission occurs may be related to the fact that these nuclei are near the limits of the more neutron rich Zr and Te nuclei observed. The ¹³⁶Te is more spherical than the heavy partners in the other pairs and this may influence the 0n channel. Finally, the 0n channel may be more enhanced in the first data with the higher ¹⁰Be energy cutoff, leading to lower excitation energy. Also, we confirmed the 3368 keV peak with the FWHM of 60 keV emitted from the moving Be particles in the Doppler effect corrected spectrum.     

基于小尺度参考辐射的便携式伽玛射线剂量(率)仪校准方法及应用

针对现有伽玛射线剂量(率)测量仪器检定方法送检距离远、周期长、效率低的不足,中国工程物理研究院核物理与化学研究所采用基于样本仪表的机器预测方法,开展了基于小尺度参考辐射的便携式伽玛剂量(率)仪遂行校准技术研究工作。最终成功地研制了一套辐射防护用伽玛射线剂量(率)仪遂行校准装置,实现了测量标准不确定度不大于5%的良好结果。为伽玛空气比释动能量值的遂行定度提出了一条全新的技术思路,为便携式伽玛剂量(率)仪的现场和野外校准提供了一种全新的示范装备。     

Predicted intensity of gamma rays from photonium

We have shown in a previous paper that stable electron-positron resonances (photonium) can account for the dark matter in the universe. In this paper we show that photonium in the galaxy will be dissociated by cosmic rays. We predict the intensity of the resulting 511 keV gamma rays as a test of the model. We find that the predictions exceed observations from the galactic center for model where the photonium has a similar distribution to the baryons. The predicted intensity is consistent with observations if the photonium is distributed in a large halo.One of us (JPV) acknowledges support from the U.S. Department of Energy under Grant DE-FG02-87ER40371, Division of High Energy and Nuclear Physics     

Contribution to the theory of parametric generation of cyclotron radiation

A linear theory of the cyclotron parametric instability in systems which are classical analogues of quantum lasers without inversion is developed. The cyclotron interaction of different types of modulated electron beams with a bichromatic field, produced by waves propagating at an angle with respect to a constant magnetic field, is investigated. It is shown that simultaneous amplification of two parametrically coupled modes with different frequencies and positive energy is possible in this system with modulation of the active and reactive components of the susceptibility of an electronic ensemble. The results obtained are important from the standpoint of the general theory of radiation processes in electron beams and plasma and for the advancement of microwave electronics.     

Experimental beta-decay energies of short-lived light fission products

The beta-decay energy of 20 nuclides in the mass region 88≦A≦102 has been measured using the on-line mass separator LOHENGRIN. The experimental values obtained are compared with theoretical predictions of different mass formulae.