Modeling of the RF system for the normal conducting linac

To study the new RF control methods, a mathematic model of the RF system for the normal conducting linac is built and implemented with the software of Matlab. The model contains some typical units of the RF system, such as the klystron, the SLED and the traveling wave accelerating tube. Finally, the model is used to study the working point of the SLED and the adaptive feed forward algorithm for the RF control system. Simulation shows that the model works well as expected.     

Design studies of a 100 MeV proton linear accelerator

Design details of a 100 MeV proton linear accelerator (Alvarez system) operating at a resonating frequency of 400 MHz have been studied. Increase in the linac operating frequency has become feasible with the possibility of injecting protons from a radio frequency quadrupole accelerator with energies higher than the conventional pre-injectors. Various electrical parameters of such a system have been calculated and compared with the existing linac injectors operating at 200 MHz.     

Physics design of a 10 MeV, 6 kW travelling wave electron linac for industrial applications

We present the physics design of a 10 MeV, 6 kW S-band (2856 MHz) electron linear accelerator (linac), which has been recently built and successfully operated at Raja Ramanna Centre for Advanced Technology, Indore. The accelerating structure is a 2π/3 mode constant impedance travelling wave structure, which comprises travelling wave buncher cells, followed by regular accelerating cells. The structure is designed to accelerate 50 keV electron beam from the electron gun to 10 MeV. This paper describes the details of electromagnetic design simulations to fix the mechanical dimensions and tolerances, as well as heat loss calculations in the structure. Results of design simulations have been compared with those obtained using approximate analytical formulae. The beam dynamics simulation with space charge is performed and the required magnetic field profile for keeping the beam focussed in the linac has been evaluated and discussed. An important feature of a travelling wave linac (in contrast with standing wave linac) is that it accepts the RF power over a band of frequencies. Three-dimensional transient simulations of the accelerating structure along with the input and output couplers have been performed using the software CST-MWS to explicitly demonstrate this feature.     

Design and simulation of a beam position monitor for the high current proton linac

In this paper, the 2-D electrostatic field software, POISSON, is used to calculate the characteristic impedance of a BPM (beam position monitor) for a high current proton linac. Furthermore, the time-domain 3-D module of MAFIA with a beam microbunch at a varying offset from the axis is used to compute the induced voltage on the electrodes as a function of time. Finally, the effect of low 13 beams on the induced voltage, the sensitivity and the signal dynamic range of the BPM are discussed.     

Preliminary design of high-power wave-guide/transmission system for multimegawatt CW requirements of 100 MeV proton LINAC

Development of a 100 MeV CW proton LINAC has been planned at CAT. This LINAC will be needing CW rf power in the frequency ranges of 350 MHz and 700 MHz for its RFQ and DTL/CCDTL/SFDTL structures respectively. The power to the accelerating structures will be produced by either 1 MW CW or 250 kW CW klystrons/inductive output tubes (HOM IOTs). The power needed by respective feed points in the structure is max. 250 kW which will be powered by splitting the power from 1 MW klystron/klystrode into four channels by using a wave-guide system. In case of using 250 kW tubes the power to the structures will be provided directly from each tube. Two types of wave-guide transmission system have been considered, viz, WR 2300 for 350 MHz rf needs and WR 1500 for 700 MHz rf needs. The typical wave-guide system has been designed using the 1 MW CW klystron followed by wave-guide filter, dual directional coupler, high-power circulator, three 3 dB magic TEE power dividers to split the main channel into four equal channels of 250 kW each. Each individual channel has dual directional couplers, flexible wave-guide sections and high power ceramic vacuum window. The circulator and each power divider is terminated into the isolated ports by high power CW loads. Out of the four channels three channels have phase shifters. Present paper describes the technological aspects and design specifications-considerations for these stringent requirements.     

Electrochemical properties of a proton conducting polymer

Electrochemical, optical and thermal characterisation of a proton conducting polymer system based on poly(2-acrylamido-2 methyl-propane-sulfonic acid) (Poly-AMPS) for use in electrochromic windows is reported. The polymer electrolyte has been obtained by cross-linking branched poly(ethylene imine) with the 2-acrylamido-2 methyl-propane-sulfonic acid. The conductivity of the poly-AMPS films is influenced by the water content in the membrane and can vary between 10⁻⁴ and 10⁻⁷ Ω⁻¹ cm⁻¹. A minimum activation energy of 17±3 kJ/mol is estimated by a simple Arrhenius model. Poly-AMPS is very sensitive to the humidity in the surroundings and electrochromic windows should be sealed if poly-AMPS is used. Temperatures above 45–50 °C give increasing cracks in the polymer and loss of adhesion to the electrode surface. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997     

AC impedance studies on proton conducting polymer electrolyte complexes (PVA+CH3COONH4)

A proton conducting polymer electrolytes of pure polyvinyl alcohol and polyvinyl alcohol complexed with ammonium acetate having different compositions have been prepared by solution cast technique. FTIR spectrum confirms the complexation process. The conductivity of the pure polyvinyl alcohol is in the order 10⁻¹⁰ S/cm at ambient temperature and its value increases 10⁴ times when complexed with 20% ammonium acetate. The Arrhenius plot for all electrolyte shows two different regions above and below the glass transition temperature. A high dielectric loss value is observed for the case of complexed PVA in comparison to pure PVA. Based on the study of relaxation spectra, it is found that the relaxation time decreases with increase in temperature and dopant concentration. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Characterisation of the bremsstrahlung generated by a 450 MeV superconducting electron linac using the inverse calculation method based on a genetic algorithm

The bremsstrahlung energy spectrum generated by the 450 MeV electron linac driving the vacuum ultra violet free electron laser FLASH (free electron laser in Hamburg) operated by DESY was measured with TLD-700 detectors and unfolded using a technique based on a genetic algorithm. The half (1/2), one-fourth (1/4) and tenth (1/10) value layer thickness of lead were estimated to be 1.0, 4.0 and 20 mm, respectively. The peak and average photon energy were calculated from the unfolded bremsstrahlung spectrum and found to be 0.5 and 0.8 MeV, respectively.     

Structural and ionic conductivity studies on proton conducting polymer electrolyte based on polyvinyl alcohol

An attempt has been made to prepare a new proton conducting polymer electrolyte based on polyvinyl alcohol (PVA) doped with NH₄NO₃ by solution casting technique. The complex formation between polymer and dissociated salt has been confirmed by X-ray diffraction analysis. The ionic conductivity of the prepared polymer electrolyte has been found by ac impedance spectroscopic analysis. The highest ionic conductivity has been found to be 7.5 × 10⁻³ Scm⁻¹ at ambient temperature for 20 mol% NH₄NO₃-doped PVA with low activation energy (~0.19 eV). The temperature-dependent conductivity of the polymer electrolyte follows an Arrhenius relationship, which shows hopping of ions in the polymer matrix.     

Preparation and characterization of crosslinked proton conducting membranes based on chitosan and PSSA-MA copolymer

Proton conducting crosslinked complex membranes were prepared by blending of a cationic polyelectrolyte, i.e. chitosan (CS) and an anionic polyelectrolyte, i.e. poly(4-styrenesulfonic acid-co-maleic acid) (PSSA-MA). In particular, the dual function of PSSA-MA as a crosslinker and a proton conductor is described. The esterification reaction between –OH of CS and –COOH of PSSA-MA and the complex formation of NH₃⁺ of CS and SO₃^? of PSSA-MA were confirmed using FT-IR spectroscopy. The ion exchange capacity (IEC) of membranes continuously increased with PSSA-MA concentrations, resulting from the increase of ionic groups. However, the membranes exhibited the minimum values of proton conductivity and water uptake at 50–67 wt.% of PSSA-MA due to the effect of crosslinking and complex formation. In addition, a maximum of Young's modulus was achieved at 50 wt.% of PSSA-MA, as revealed by universal testing machine (UTM). Thermogravimetric analysis (TGA) showed that the thermal stability of membranes increased with increasing PSSA-MA concentrations and was the highest at 50 wt.% of PSSA-MA.     

Physics design of a CW high-power proton Linac for accelerator-driven system

Accelerator-driven systems (ADS) have evoked lot of interest the world over because of their capability to incinerate the MA (minor actinides) and LLFP (long-lived fission products) radiotoxic waste and their ability to utilize thorium as an alternative nuclear fuel. One of the main subsystems of ADS is a high energy (∼1 GeV) and high current (∼30 mA) CW proton Linac. The accelerator for ADS should have high efficiency and reliability and very low beam losses to allow hands-on maintenance. With these criteria, the beam dynamics simulations for a 1 GeV, 30 mA proton Linac has been done. The Linac consists of normal-conducting radio-frequency quadrupole (RFQ), drift tube linac (DTL) and coupled cavity drift tube Linac (CCDTL) structures that accelerate the beam to about 100 MeV followed by superconducting (SC) elliptical cavities, which accelerate the beam from 100 MeV to 1 GeV. The details of the design are presented in this paper.     

Hydrogenation of carbon dioxide in a proton conducting cell reactor

The CO₂-H₂ reaction was studied at 723–973 K and atmospheric total pressure using a proton conducting double-chamber cell-reactor. The proton conductor was a strontia-ceria-ytterbia (SCY) perovskite of the form: SrCe_0.95Yb_0.05O_3−α. Palladium films served as cathodic and anodic electrodes. CO₂/He mixtures were introduced over the cathodic electrode while high-purity hydrogen was passing over the anode. The effects of both the imposed current and the inlet gas composition on the reaction rates and product distribution were examined. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.     

Study on the characteristics of linac based THz light source

There are many methods based on linac for THz radiation production.As one of the options for the Beijing Advanced Light, an ERL test facility is proposed for THz radiation.In this test facility, there are 4 kinds of methods to produce THz radiation: coherent synchrotron radiation (CSR), synchrotron radiation (SR), low gain FEL oscillator, and high gain SASE FEL.In this paper, we study the characteristics of the 4 kinds of THz light sources.     

Design and simulation of a wire scanner for the CSNS linac

In this paper,we report the design and simulation of a wire scanner for the linac of the CSNS(China Spallation Neutron Source).The wire scanner is used to measure the transverse beam profile andthe emittance.The effect of beam energy change upon the mechanical design of the wire scanner must beconsidered.The simulation results of heat on the two specified wires,tungsten and carbon,by using the finite element method software,ANSYS,are presented.In addition,the effect of wire deformation on the beam profile measurement is qualitatively analyzed,and the signal level of the wire scanner is discussed.     

Study of ammonia decomposition in a proton conducting solid electrolyte cell

The reaction of NH₃ decomposition was studied at 500–700 °C and atmospheric total pressure using a single-chamber cell-reactor. The proton conductor was a strontia-ceria-ytterbia (SCY) perovskite of the form: SrCe_0.95Yb_0.05O_3−α. Silver films served as cathodic and anodic electrodes. The effects of imposed current, temperature and inlet gas composition on the reaction rate were examined. Paper presented at the 8th EuroConference on Ionics, Carvoeire, Algarve, Portugal, Sept. 16–22, 2001.     

A CW CO chemical laser based on a hollow-cathode discharge

We report on a small-scale CW chemical CO laser using a hollow-cathode discharge for atomic oxygen production. This kind of discharge exhibits several unique properties which make it an ideal source of atomic oxygen. The construction and operation are simple and the design very compact. A specific laser energy of 100 J g^-1 and laser outputs of 9 W were obtained with an active length of 7.5 cm.     

Beam stability investigation for a free electron lithographic laser based on an energy-recovery linac

According to leading producers of microelectronic devices, lithography based on free electron lasers (FEL) could become the main technology for the mass production of elements with a scale up to 5 nm in the near future. One of the main hindrances in this path is the absence of working FEL with the required parameters. A feasibility study devoted to the production of such an FEL based on a superconducting energyrecovery linac (ERL) has been carried out at the Budker Institute of Nuclear Physics (BINP). The ERL average current is limited by longitudinal and transverse instabilities, caused by the interaction of an electron beam with the fields induced by it in the superconducting cavities. The estimations of the threshold currents and parameters of the ERL required for the operation of FEL are obtained.     

On the use of Pd filters on proton conducting SOFC ceramics

Ceramic proton conductors are materials which conduct protons under an applied electric field and permit the construction of a SOFC in analogy to the oxygen ion conductor 8YSZ. Such protonic ceramic fuel cells have been labelled PCFCs to distinguish them from the standard SOFCs. PCFCs have several advantages when compared with standard SOFCs. First, there is no water contamination of the fuel gas. Second, the protonic conductivity may be higher in the intermediate temperature range (550 to 700 °C). Also, the activation energy for proton migration is much lower than that of oxygen ion conduction. In addition, internal reforming is also possible permitting the use of natural gas. An intriguing possibility is the use of palladium filters on the fuel side which only permit the diffusion of protons to the filter-electrolyte interface. This may reduce undesirable mixing of the fuel and the oxygen on either side of the electrolyte. In this work, it is shown that the entry of protons from the Pd into the ceramic conductor is straightforward. Prototype test PCFCs are shown to operate as required. To test the Pd - ceramic proton conductor system a study was undertaken using Pd tubes which were coated with thin layers of the proton conducting ceramics. When flushing the tube insides with hydrogen and exposing the outsides to air, Nernst voltages of such electrochemical cells could be recorded as a function of temperature. The present rather preliminary work, however, was hampered by leakage of the thin film HTPC's. Thus, the theoretical Nernst voltages were not attained. Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002.     

18 MeV质子辐照对TiNi形状记忆合金R相变的影响

研究了用HZ B串列加速器的18MeV质子辐照对TiNi形状记忆合金R相变的影响,辐照在奥氏体母相状态下进行。示差扫描量热法(DSC)表明,辐照后R相变开始温度TsR和逆马氏体相变结束温度TfA随辐照注量的增加而降低。当注量为1.53×1014/cm2时,TsR和TfA分别下降6K和13K,辐照未引起R相变结束温度TfR和逆马氏体相变开始温度TsA的变化。表明辐照后母相(奥氏体相)稳定。透射电镜(TEM)分析表明辐照后没有引起合金可观察的微观组织变化。辐照对R相变开始温度TsR和逆马氏体相变结束温度Af的影响可能是由于质子辐照后产生了孤立的缺陷团,形成了局部应力场,引起晶格有序度的下降所造成的。