Application of photovoltaic electric power to the rural education/communication needs of developing countries

The suitability (i.e., cost competitiveness and reliability) of photovoltaic (PV) power systems for rural applications in developing countries is considered. Potential application sectors include health delivery, education and communication where small amounts of electricity are needed to meet critical needs

Case report

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R&D ERL: SRF Electron Gun

When the BNL high current ERL was first envisioned the choice of injector went through several iterations before concluding that an SRF injector was the appropriate choice for the task at hand. The design requirements were quite stringent as the injector had to be designed to reach currents never before achieved in any injector. The overall goal was to design an injector capable of delivering up to 0.5 Ampere at 703.75 MHz. This criteria was set based on the need to demonstrate high average current energy recovery at the ERL so that future machines could be designed and built with confidence in the injector. For the ERL the injector needs to be capable of accelerating electrons to 2-2.5 MeV with charges ranging from 0.7 to 5 nC per bunch depending on the operational parameters being studied. These criteria led to a 1/2 cell photoinjector designed to accommodate a demountable photocathode utilizing a novel quarter wave choke joint for the cathode insertion mechanism. The cavity requires a total of 1 MW of power coupled to the beam in order to meet the high current application, necessitating two 500 kW RF power couplers. This AP note will review the overall physics design and analysis, the fabrication sequence, and the testing plan for this cavity

Energy Recovery Linac: SRF Electron Gun

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CHALLENGES ENCOUNTERED DURING THE PROCESSING OF THE BNL ERL 5 CELL ACCELERATING CAVITY

One of the key components for the Energy Recovery Linac being built by the Electron cooling group in the Collider Accelerator Department is the 5 cell accelerating cavity which is designed to accelerate 2 MeV electrons from the gun up to 15-20 MeV, allow them to make one pass through the ring and then decelerate them back down to 2 MeV prior to sending them to the dump. This cavity was designed by BNL and fabricated by AES in Medford, NY. Following fabrication it was sent to Thomas Jefferson Lab in VA for chemical processing, testing and assembly into a string assembly suitable for shipment back to BNL for integration into the ERL. The steps involved in this processing sequence will be reviewed and the deviations from processing of similar SRF cavities will be discussed. The lessons learned from this process are documented to help future projects where the scope is different from that normally encountered

Energy Recovery Linac: 5 Cell 704 MHz SRF Cavity

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MULTIPACTING ANALYSIS OF A QUARTER WAVE CHOKE JOINT USED FOR INSERTION OF A DEMOUNTABLE CATHODE INTO A SRF PHOTOINJECTOR

The multipacting phenomena in accelerating structures and coaxial lines are well documented and methods of mitigating or suppressing it are understood. The multipacting that occurs in a quarter wave choke joint designed to mount a cathode insertion stalk into a superconducting RF photoinjector has been analyzed via calculations and experimental measurements and the effect of introducing multipacting suppression grooves into the structure is analyzed. Several alternative choke joint designs are analyzed and suggestions made regarding future choke joint development. Furthermore, the problems encountered in cleaning the choke joint surfaces, factors important in changes to the secondary electron yield, are discussed and evaluated. This design is being implemented on the BNL 1.3 GHz photoinjector, previously used for measurement of the quantum efficiency of bare Nb, to allow for the introduction of other cathode materials for study, and to verify the design functions properly prior to constructing our 703 Mflz photoinjector with a similar choke joint design

High power RF input couplers and test stand for the BERLinPro Project

The bERLinPro project [1], under construction at HZB, is a 100 mA, 50 MeV superconducting RF SRF energy recovery linac ERL being built to study the accelerator technology and physics of operating a high current SRF ERL. For this high current operation, coaxial RF power couplers capable of handling 115 kW of power per coupler, dual couplers per cavity , continuous wave cw at 1.3 GHz are required for both the SRF photo injector and booster cavities. In order to sustain this power level a coupler has been designed based on the high power coupler currently in use at the KEK cERL. Two key changes that were made to the coupler were the modification of the coupler tip, termed a golf tee, as well as increased cooling of the inner conductor. This former modification is incorporated so as to achieve the desired coupling, Qext 105, with minimal coupler penetration into the beam pipe. Herein, we discuss the RF design and properties of the high power coaxial coupler for the photo injector as well as booster cavities of bERLinPro, along with the design of the test stand for conditioning a pair of coupler

Commissioning results of the HZB Quadrupole Resonator

Recent cavity results with niobium have demonstrated the necessity of a good understanding of both the BCS and residual resistance. For a complete picture and comparison with theory, it is essential that one can measure the RF properties as a function of field, temperature, frequency and ambient magnetic field. Standard cavity measurements are limited in their ability to change all parameters freely and in a controlled manner. On the other hand, most sample measurement setups operate at fairly high frequency, where the surface resistance is always BCS dominated. The quadrupole resonator, originally developed at CERN, is ideally suited for characterization of samples at typical cavity RF frequencies. We report on a modified version of the QPR with improved RF figures of merit for high field operation. Experimental challenges in the commissioning run and alternate designs for simpler sample changes are shown alongside measurement results of a large grain niobium sampl

RF input power couplers for high current SRF applications

present day accelerator science. The bERLinPro project is presently being built at HZB to address the challenges involved in high current SRF machines with the goal of generating and accelerating a 100 mA electron beam to 50 MeV in continuous wave cw mode at 1.3 GHz. One of the main challenges in this project is that of handling the high input RF power required for the photo injector as well as booster cavities where there is no energy recovery process. A high power co axial input power coupler is being developed to be used for the photo injector and booster cavities at the nominal beam current. The coupler is based on the KEK cERL design and has been modified to minimise the penetration of the coupler tip in the beam pipe without compromising on beam power coupling Qext 105 . Herein we report on the RF design of the high power 115 kW per coupler, dual couplers per cavity bERLinPro BP coupler along with initial results on thermal calculations. We summarise the RF conditioning of the TTF III couplers modified for cw operation performed in the past at BESSY HZB. A similar conditioning is envisaged in the near future for the low current SRF photo injector and the bERLinPro main linac cryomodule