Volume 80, Issue 12, December 2009
Index of content:
- PARTICLE SOURCES, OPTICS AND ACCELERATION; PARTICLE DETECTORS
80(2009); http://dx.doi.org/10.1063/1.3262501View Description Hide Description
We report a multipurpose furnace designed for studies using synchrotron radiation on polycrystalline materials, namely, metals, ceramics, and (semi)crystalline polymers. The furnace has been designed to carry out three-dimensional (3D) x-ray diffractionmeasurements but can also be used for other types of synchrotron radiation research. The furnace has a very low thermal gradient across the specimen . Accurate determination of the temperature can be carried out by welding a thermocouple to the specimen. The furnace can be rotated over an angle of 90° in order to determine the crystallographic orientation of each individual grain. It is possible to follow growth kinetics of all grains in the illuminated volume of the specimen. The specimen environment can be controlled varying from vacuum (up to ) to gas or air filled. The maximum temperature of operation is , with the possibility of achieving high heating (up to ) and cooling rates (up to without quenching gas). 3D maps of the microstructure of the specimen can be generated at elevated temperatures by bringing the high-resolution detector close to the specimen. We show an example of a simulation of the heat affected zone during the thermal cycle of a weld in a transformation-induced plasticity steel carried out using the furnace. The unique characteristics of the furnace open possibility of new fields in materials research using synchrotron radiation.
80(2009); http://dx.doi.org/10.1063/1.3271537View Description Hide Description
The quality factor of a superconducting NbTi resonator at 1.6 MHz in a magnetic field up to 1.2 T as well as its temperature dependence is investigated. A hysteresis effect in the superconductingsurfaceresistance as a function of the magnetic field is observed. An unloaded -value of the resonator of 40 500 is achieved at 3.9 K. It is shown that this -value is limited by dielectric losses in the FORMVAR insulation of the coils wire. The details of the -value optimization are discussed. In the temperature dependence of the -value a steep decrease is observed above . Finally, the implications of these measurements for real trap experiments are discussed in detail.
80(2009); http://dx.doi.org/10.1063/1.3272784View Description Hide Description
A new particle sizer which integrates the dispersion and detection parts is presented. Particles are dispersed based on charging between two parallel plates connected to a high voltage power source. The charged particles bounce between the two plates and escape into a measuring area where the size is determined by light scattering. The instrument is calibrated using standard powders. The data obtained from the new instrument are in good agreement with those obtained from a commercial particle size analyzer. The sizer works both for insulator and conductive powders.
80(2009); http://dx.doi.org/10.1063/1.3272789View Description Hide Description
X-ray generation based on laser-electron Compton scattering is one attractive method to achieve a compact laboratory-sized high-brightness x-ray source. We have designed, built, and tested such a source; it combines a 50 MeV multibunch electron linac with a mode-locked 1064 nm laser stored and amplified in a Fabry–Pérot optical cavity. We directly observed trains of pulsed x rays using a microchannel plate detector; the resultant yield was found to be in good agreement with prediction. We believe that the result has demonstrated good feasibility of linac-based compact x-ray sources via laser-electron Compton scatterings.
High intensity electron cyclotron resonance proton source for low energy high intensity proton accelerator80(2009); http://dx.doi.org/10.1063/1.3272786View Description Hide Description
Electron cyclotron resonance (ECR) protonsource at 50 keV, 50 mA has been designed, developed, and commissioned for the low energy high intensity proton accelerator (LEHIPA). Plasma characterization of this source has been performed. ECR plasma was generated with 400–1100 W of microwave power at 2.45 GHz, with hydrogen as working gas. Microwave was fed in the plasmachamber through quartz window. Plasma density and temperature was studied under various operating conditions, such as microwave power and gas pressure. Langmuir probe was used for plasma characterization using current voltage variation. The typical hydrogen plasma density and electron temperature measured were and 6 eV, respectively. The total ion beam current of 42 mA was extracted, with three-electrode extraction geometry, at 40 keV of beam energy. The extracted ion current was studied as a function of microwave power and gas pressure. Depending on source pressure and discharge power, more than 30% total gas efficiency was achieved. The optimization of the source is under progress to meet the requirement of long time operation. The source will be used as an injector for continuous wave radio frequency quadrupole, a part of 20 MeV LEHIPA. The required rms normalized emittance of this source is less than . The simulated value of normalized emittance is well within this limit and will be measured shortly. This paper presents the study of plasma parameters, first beam results, and the status of ECR protonsource.