Neutron Capture Therapy (NCT) & In-Hospital Neutron Irradiator (IHNI)——a new technology on binary targeting radiation therapy of cancer

BNCT is finally becoming "a new option against cancer".The difficulties for its development progress of that firstly is to improve the performance of boron compounds,secondly,it is the requirements of quantification and accuracy upon radiation dosimetry evaluation in clinical trials.Furthermore,that is long anticipation on hospital base neutron sources.It includes dedicated new NCT reactor,accelerator based neutron sources,and isotope source facilities.In addition to reactors,so far,the technology of other types of sources for clinical trials is not yet completely proven.The In-Hospital Neutron Irradiator specially designed for NCT,based on the MNSR successfully developed by China,can be installed inside or near the hospital and operated directly by doctors.The Irradiator has two neutron beams for respective treatment of the shallow and deep tumors.It is expected to initiate operation in the end of this year.It would provide a safe,low cost,and effective treatment tool for the NCT routine application in near future.

Neutron irradiation influence on high-power thyristor device under fusion environment

Because of their economy and applicability,high-power thyristor devices are widely used in the power supply systems for large fusion devices.When high-dose neutrons produced by deuterium–tritium(D–T)fusion reactions are irradiated on a thyristor device for a long time,the electrical characteristics of the device change,which may eventually cause irreversible damage.In this study,with the thyristor switch of the commutation circuit in the quench protection system(QPS)of a fusion device as the study object,the relationship between the internal physical structure and external electrical parameters of the irradiated thyristor is established.Subsequently,a series of targeted thyristor physical simulations and neutron irradiation experiments are conducted to verify the accuracy of the theoretical analysis.In addition,the effect of irradiated thyristor electrical characteristic changes on the entire QPS is studied by accurate simulation,providing valuable guidelines for the maintenance and renovation of the QPS.

Comparison of neutron irradiation effects on the electrical performances of SiGe HBT and SiBJT

The change of electrical performances of silicon-germanium (SiGe)heterojunction bipolar transistor (HBT) and Si bipolar junction transistor (BJT) was studied as afunction of reactor fast neutron radiation fluence. Alter neutron irradiation, the collector currentI_c and the current gain beta decrease, and the base current I_b increases generally for SiGe HBT.The higher the neutron irradiation fluence is, the larger I_b increases. For conventional Si BJT,I_c and I_b increase as well as beta decreases much larger than SiGe HBT at the same fluence. It isshown that SiGe HBT has a larger anti-radiation threshold and better anti-radiation performance thanSi BJT. The mechanism of performance changes induced by irradiation was preliminarily discussed.

Determination of Neutron Irradiation-Induced Phosphorus Segregation on Grain Boundaries in a P-doped 2.25Cr1Mo Steel

Irradiation-induced impurity segregation to grain boundaries is one of the important radiation effects on materials. For this reason, phosphorus segregation to prior austenite grain boundaries in a P-doped 2.25Cr1Mo steel subjected to neutron irradiation is examined using field emission gun scanning transmission electron microscopy (FEGSTEM) with energy dispersive X-ray microanalysis (EDX). The steel samples are irradiated around 270 and 400℃, respectively. The irradiation dose rate and dose are -1.05×10-8 dpa/s and -0.042 dpa respectively for 270℃ irradiation, and 1.7×10-8 dpa/s and 0.13 dpa respectively for 400℃ irradiation. The FEGSTEM results indicate that there is no apparent phosphorus segregation during 270℃ irradiation but there is some during 400℃ irradiation.

Neutron irradiation-induced effects on the reliability performance of electrochemical metallization memory devices

In this work,electrochemical metallization memory(ECM)devices with an Ag/AgInSbTe(AIST)/amorphous carbon(a-C)/Pt structure were irradiated with 14 MeV neutrons.The switching reliability performance before and after neutron irradiation was compared and analyzed in detail.The results show that the irradiated memory cells functioned properly,and the initial resistance,the resistance at the low-resistance state(LRS),the RESET voltage and the data retention performance showed little degradation even when the total neutron fluence was as high as 2.5×1011 n/cm2.Other switching characteristics such as the forming voltage,the resistance at the high-resistance state(HRS),and the SET voltage were also studied,all of which merely showed a slight parameter drift.Irradiation-induced Ag ions doping of the a-C layer is proposed to explain the damaging effects of neutron irradiation.The excellent hard characteristics of these Ag/AIST/a-C/Pt-based ECM devices suggest potential beneficial applications in the aerospace and nuclear industries.

Neutron irradiation effects on AlGaN/GaN high electron mobility transistors

A1GaN/GaN high electron mobility transistors （HEMTs） were exposed to 1 MeV neutron irradiation at a neutron ftuence of 1 × 10^15 cm-2. The dc characteristics of the devices, such as the drain saturation current and the maximum transconductance, decreased after neutron irradiation. The gate leakage currents increased obviously after neutron irradiation. However, the rf characteristics, such as the cut-off frequency and the maximum frequency, were hardly affected by neutron irradiation. The A1GaN/GaN heterojunctions have been employed for the better understanding of the degradation mechanism. It is shown in the Hall measurements and capacitance voltage tests that the mobility and concentration of two-dimensional electron gas （2DEG） decreased after neutron irradiation. Tbere was no evidence of the full-width at half-maximum of X-ray diffraction （XRD） rocking curve changing after irradiation, so the dislocation was not influenced by neutron irradiation. It is concluded that the point defects induced in A1GaN and GaN by neutron irradiation are the dominant mechanisms responsible for performance degradations of A1GaN/GaN HEMT devices.

The effects of fast neutron irradiation on oxygen in Czochralski silicon

The effects of fast neutron irradiation on oxygen atoms in Czochralski silicon （CZ-Si） are investigated systemically by using Fourier transform infrared （FTIR） spectrometer and positron annihilation technique （PAT）. Through isochronal annealing, it is found that the trend of variation in interstitial oxygen concentration （[Oi]） in fast neutrons irradiated CZ-Si fluctuates largely with temperature increasing, especially between 500 and 700℃. After the CZ-Si is annealed at 600℃, the V4 appearing as three-dimensional vacancy clusters causes the formation of the molecule-like oxygen clusters, and more importantly these dimers with small binding energies （0.1-1.0eV） can diffuse into the Si lattices more easily than single oxygen atoms, thereby leading to the strong oxygen agglomerations. When the CZ-Si is annealed at temperature increasing up to 700℃, three-dimensional vacancy clusters disappear and the oxygen agglomerations decompose into single oxygen atoms （O） at interstitial sites. Results from FTIR spectrometer and PAT provide an insight into the nature of the [Oi] at temperatures between 500 and 700℃. It turns out that the large fluctuation of [Oi] after short-time annealing from 500 to 700℃ results from the transformation of fast neutron irradiation defects.

Accelerated oxygen precipitation in fast neutron irradiated Czochralski silicon

Annealing effect of the oxygen precipitation and the induced defects have been investigated on the fast neutron irradiated Czochralski silicon （CZ-Si） by infrared absorption spectrum and the optical microscopy. It is found that the fast neutron irradiation greatly accelerates the oxygen precipitation that leads to a sharp decrease of the interstitial oxygen with the annealing time. At room temperature （RT）, the 1107cm^-1 infrared absorption band of interstitial oxygen becomes weak and broadens to low energy side. At low temperature, the infrared absorption peaks appear at 1078cm^-1, 1096cm^-1, and 1182cm^-1, related to different shapes of the oxygen precipitates. The bulk microdefects, including stacking faults, dislocations and dislocation loops, were observed by the optical microscopy. New or large stacking faults grow up when the silicon self-interstitial atoms are created and aggregate with oxygen precipitation.

Synergistic effects of neutron and gamma ray irradiation of a commercial CHMOS microcontroller

This paper presents the experimental results of a combined irradiation environment of neutron and gamma rays on 80C196KC20, which is a 16-bit high performance member of the MCS96 microcontroller family. The electrical and functional tests were made in three irradiation environments： neutron, gamma rays, combined irradiation of neutron and gamma rays. The experimental results show that the neutron irradiation can affect the total ionizing dose behaviour. Compared with the single radiation environment, the microcontroller exhibits considerably more severe degradation in neutron and gamma ray synergistic irradiation. This phenomenon may cause a significant hardness assurance problem.

THE LATE EFFECTS ON BONE MARROWS IN MICE AFTER TOTAL BODY IRRADIATION BY P(35) BE FAST NEUTRONS AND γ RAYS

Purpose: To understand the late effects on bonemarrow after widefield or total body irrdiation withvarious types of radiation.Materials and Methods: Total body irradiationwith single dose of P(35) Be fast Neutrons and γ raysrespectively have been used in this study. Kunming strainmice were irradiated by fast neutrons produced bybombardment of beryllium target with 35MeV protonsand the dose rate was 0.12 to 0.14 Gy/min. Nine doselevels were used in fast neutrons irradiation from 0.20 to3.50Gy. The dose rate of 60Co γ rays was 0.60Gy/min andirradiation was in the range of 0.25 to 9.00Gy. Sixteendose points were studied. All animals without anesthesiawere irradiated whole body with single doses by fastneutrons and γ rays respectively, One group withoutirradiation was regarded as control group. 90 days afterirradiation all animals were sacrificed. The nucleatedcells of bone marrow and the peripheral blood cellsincluding WBC and lymphocytes were counted.Results: our study shows that the number ofnucleated cells of bone marrow in both fast neutrons andγ ray groups decreased with increase of the doses. Thereare significant differences between irradiated groups andzero line (control group) and the slopes are -1.41 ±0.55(p=0.038) and -0.98 ± 0. 24(P= 0.0015) for fast neutronsand γ rays respectively. There is no significant differencebetween the two kinds of radiation (p>0.05). The lateeffects on peripheral blood cells (WBC and lymphocytes)in mice after irradiation with single doses of neutrons andγ rays were signincantly lower than unirradiated group(P< 0.05). However, the dependence of the values ofperipheral blood cells on doses is not found and there areno significant differences between neutrons and γ raysgroups.Conclusions: Total body irradiation with neutronsor γ rays can suppress marrow in mice in the long-term,and is more obvious with increase of doses. There is nosignificant difference between neutrons and γ rays for thelate effects studied.

Characteristics of Positron Trapping at Defects in Neutron－irradiated Silicon Grown in Argon Atmosphere

The positron lifetime spectroscopy and Doppler-broadening measurements indicate that there alwaysare some V-type defects in FZ Si during annealing from room temperature to 1150℃ . In NTD (neutrontransmutation doped) Si irradiated by 6×10￣(16) neutrons/ cm￣2 the main defect is V-type, the V_2 defectshave only an intensity of 7.3% and anncal out at the temperature lower than 200℃ . In NTD Si irradiatedby 1.2×10￣(18) neutrons/cm￣2 the intensities due to V- and V_2type defects are 59% and 35%. The formerdisappears at 55℃ . the latter increases above 200℃ , decreases greatly above 550℃ , and disappears at650℃ . In addition, V_4 appears at 125～200℃, V_4 and / or V_5 defects at 400～600℃ in high-dose irradiated NTD Si. It seems that radiation doses have a bigger influence on the formation and annealing behaviorof secondary V_2type defects. Above 700℃ a lot of dislocations and / or monovacancy-type defects are formed.

Analysis of multiple cell upset sensitivity in bulk CMOS SRAM after neutron irradiation

In our previous studies, we have proved that neutron irradiation can decrease the single event latch-up （SEL） sensitivity of CMOS SRAM. And one of the key contributions to the multiple cell upset （MCU） is the parasitic bipolar amplification, it bring us to study the impact of neutron irradiation on the SRAM＇s MCU sensitivity. After the neutron experiment, we test the devices＇ function and electrical parameters. Then, we use the heavy ion fluence to examine the changes on the devices＇ MCU sensitivity pre- and post-neutron-irradiation. Unfortunately, neutron irradiation makes the MCU phenomenon worse. Finally, we use the electric static discharge （ESD） testing technology to deduce the experimental results and find that the changes on the WPM region take the lead rather than the changes on the parasitic bipolar amplification for the 90 nm process.

Radiation Damage and Recovery in Neutron-Irradiated MgO Crystal

MgO single crystal was irradiated by neutron up to a dose of 5.74×1018 cm-2. The radiation damage and its recovery were studied by means of UV-VIS and EM spectroscopy. The results indicate that the irradiation generates large amount of optically detectable defects such as single anion vacancies (F+ center), anion divacancies (F2) and some higher order defects. Through isochronal annealing, these defects started a series of processes of diminishing and transforming, and finally all disappeared while annealing at 900 ℃. It seems that the absorption bands of 573 nm are resulted from a higher order and more complex aggregated center than that of 424, 451 nm bands.

Influence of Fast Neutron Irradiation on Critical Current Densities of Bi-2223/Ag Tape

Experimental results on the magnetic field behavior of the critical current in silver sheathed Bi-2223 tapes are presented. The experiments consist of transport and magnetic measurements in a wide temperature range and in external magnetic field up to 6 T. Significant enhancement of the intragrain critical current densities Jc are observed after irradiation with fast neutron. This is attributed to an improvement of flux pinning capability by the neutron induced defects, but the weak link structure is somewhat damaged as evidenced by the small degradation of transport critical current at low field. According to the measurement of remanent magnetic moment before and after irradiation with fast neutron, the connectivity in Bi-2223 tapes is reduced by 50% after irradiated to a fluence of 2 × 1021 m-2, which resulted in the critical currents degradated by a factor of 10%.

Defects in Fast-Neutron Irradiated Nitrogen-Doped Czochralski Silicon after Annealing at High Temperature

Fast-neutron irradiated nitrogen-doped Czochralski silicon (NCZ-Si) was annealed at 1100 ℃ for different time, then FTIR and optical microscope were used to study the behavior of oxygen. It is found that [Oi] increase at the early stage then decrease along with the increasing of anneal time. High density induced-defects can be found in the cleavage plane. By comparing NCZ-Si with Czochralski silicon (CZ-Si), [Oi] in NCZ-Si decrease more after anneal 24 h.

Neutron Irradiation of Electronic Materials at HANARO

HANARO, a 30 MW open-pool type multipurpose research reactor, has been operated as a platform for nuclear researches in Korea, and irradiation facilities have been mainly utilized for various nuclear material irradiation tests requested by users. Although most irradiation tests have been related to national R&D relevant to nuclear power, demand for neutron irradiation of electro-magnetic materials is increasing rapidly at HANARO. Another research reactor, which is named the KIJANG research reactor (KJRR), is under construction in Korea. KJRR is dedicated to increasing the national radio-isotopes supply capacity and to the irradiation facilities including Neutron Transmutation Doping (NTD) facilities for power semiconductor production in a large scale and fast neutron irradiation (FNI) facility for fast neutron irradiation. The NTD and FNI facilities in the KJRR reactor can be effectively utilized on the study of separated effect of thermal and fast neutron irradiations on the properties of electro-magnetic materials. HANARO will also specialize more on irradiation research, including neutron irradiation of electronic materials. The research status and possibility of new electro-magnetic materials using neutron irradiation at HANARO are surveyed to ascertain the utilization of neutron irradiation technology in electro-magnetic material researches.

An optical study of the D-D neutron irradiation-induced defects in Co-and Cu-doped ZnO wafers

Room-temperature photoluminescence and optical transmittance spectroscopy of Co-doped（1×1014,5×1016,and 1×1017cm-2） and Cu-doped（5×1016cm-2） ZnO wafers irradiated by D-D neutrons（fluence of 2.9×1010 cm-2） have been investigated.After irradiation,the Co or Cu metal and oxide clusters in doped ZnO wafers are dissolved,and the wu¨rtzite structure of ZnO substrate for each sample remains unchanged and keeps in high c-axis preferential orientation.The degree of irradiation-induced crystal disorder reflected from the absorption band tail parameter（E0） is far greater for doped ZnO than the undoped one.Under the same doping concentration,the Cu-doped ZnO wafer has much higher irradiation-induced disorder than the Co-doped one.Photoluminescence measurements indicate that the introduction rate of both the zinc vacancy and the zinc interstitial is much higher for the doped ZnO wafer with a high doping level than the undoped one.In addition,both crystal lattice distortion and defect complexes are suggested to be formed in doped ZnO wafers.Consequently,the Co-or Cu-doped ZnO wafer（especially with a high doping level） exhibits very low radiation hardness compared with the undoped one,and the Cu-doped ZnO wafer is much less radiation-hard than the Co-doped one.

Evaluation of UV Optical Fibers Behavior under Neutron Irradiation

Degradation of UV transmitting optical fibers under nuclear reactor neutron exposure is reported. Four type of optical fibers (solarization resistant, H2-loaded;UV transmission standard OH;UV enhanced transmission, high OH, H2-loaded;high OH, deep UV enhanced) were exposed to neutron fluences up to 4 x 1017 n/cm2. The optical transmission was measured off-line over the 200 nm – 900 nm spectral range and the build-up of color centers was monitored.

Assessment of neutron-irradiated 3C-SiC implanted at 800 ℃

The favourable physical properties of SiC make it a potential material for use as containment layer in new generation nuclear reactors.The material will thus be exposed to high temperatures and fluences from fission products.The impact of increasing neutron fluence at constant irradiation temperature(800℃)on the properties of neutron-irradiated 3C-SiC was investigated,employing infrared reflectance spectroscopy and atomic force spectroscopy.A relation was found between the neutron fluence and the surface morphology of the irradiated 3CSiC.The varying surface morphology also affected the dielectric parameters of the SiC.

Annealing behaviors of vacancy in varied neutron irradiated Czochralski silicon

The difference of annealing behaviors of vacancy-oxygen complex (VO) in varied dose neutron irradiated Czochralski silicon: (S1 5×1017 n/cm3 and S2 1.07×1019 n/cm3) were studied. The results show that the VO is one of the main defects formed in neutron irradiated Czochralski silicon (CZ-Si). In this defect, oxygen atom shares a vacancy, it is bonded to two silicon neighbors. Annealed at 200 ℃, divacancies are trapped by interstitial oxygen(Oi) to form V2O (840 cm-1). With the decrease of the 829 cm-1 (VO) three infrared absorption bands at 825 cm-1 (V2O2), 834 cm-1 (V2O3) and 840 cm-1 (V2O) will rise after annealed at temperature range of 200-500 ℃. After annealed at 450-500 ℃ the main absorption bands in S1 sample are 834 cm-1, 825 cm-1 and 889 cm-1 (VO2), in S2 is 825 cm-1. Annealing of A-center in varied neutron irradiated CZ-Si is suggested to consist of two processes. The first is due to trapping of VO by Oi in low dose neutron irradiated CZ-Si (S1) and the second is due to capture the wandering vacancy by VO, etc, in high dose neutron irradiated CZ-Si (S2), the VO2 plays an important role in the annealing of A-center. With the increase of the irradiation dose, the annealing behavior of A-center is changed.