Download or read book Performance of Superconducting Cavities for CEBAF written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Continuous Electron Beam Accelerator Facility (CEBAF) is presently under construction in Newport News, Virginia. The accelerator consists of [approx]160 meters of 5-cell niobium cavities manufactured from high thermal conductivity niobium with RRR values> 250. After an initial six-month period of first article manufacturing at a rate of 3 cavities per month, the full production rate of 12 cavities per month was reached in October 1990. These cavities are chemically treated at CEBAF, assembled into hermetically sealed cavity pairs and tested in a vertical configuration prior to installation into the accelerator. The performance of all cavities received from the manufacturer and tested at CEBAF has exceeded CEBAF's design criteria for Q value> 2.4 x 10[sup 9] at 2 K and an accelerating gradient E[sub acc]> 5 MV/m. Q[sub 0] values as high as 10[sup 10] and accelerating gradients of E[sub acc] [ge] 18 MV/m have been achieved.
Download or read book Performance and Installation Status of Superconducting Cavities at CEBAF August 1992 written by C. Reece and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bericht ber den 5 internationalen Kongress zur Bek mpfung des Missbrauchs geistiger Getr nke zu Basel 20 22 August 1895 written by and published by . This book was released on 1895 with total page 562 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analysis of Performance Limitations for Superconducting Cavities written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The performance of superconducting cavities in accelerators can be limited by several factors, such as: field emission, quenches, arcing, rf power; and the maximum gradient at which a cavity can operate will be determined by the lowest of these limitations for that particular cavity. The CEBAF accelerator operates with over 300 cavities and, for each of them, the authors have determined the maximum operating gradient and its limiting factor. They have developed a model that allows them to determine the distribution of gradients that could be achieved for each of these limitations independently of the others. The result of this analysis can guide an R & D program to achieve the best overall performance improvement. The same model can be used to relate the performance of single-cell and multi-cell cavities.
Download or read book Superconducting Cavity Tuner Performance at CEBAF written by and published by . This book was released on 1993 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: At the Continuous Electron Beam Accelerator Facility (CEBAF), a 4 GeV, multipass CW electron beam is to be accelerated by 338 SRF, 5-cell niobium cavities operating at a resonant frequency of 1497 MHz. Eight cavities arranged as four pairs comprise a cyromodule, a croygenically isolated linac subdivision. The frequency is controlled by a mechanical tune attached to the first and fifth cell of the cavity which elastically deforms the cavity and thereby alters its resonant frequency. The tuner is driven by a stepper motor mounted external to the cryomodule that transfers torque through two rotary feedthroughs. A linear variable differential transducer (LVDT) mounted on the tuner monitors the displacement, and two limit switches interlock the movement beyond a 400 kHz bandwidth. Since the cavity has a loaded Q of 6.6 · 106, the control system must maintain the frequency of the cavity to within " 50 Hz of the drive frequency for efficient coupling. This requirement is somewhat difficult to achieve since the difference in thermal contractions of the cavity and the tuner creates a frequency hystersis of approximately 10 kHz. The cavity is also subject to frequency shifts due to pressure fluctuations of the helium bath as well as radiation pressure. This requires that each cavity be characterized in terms of frequency change as a function of applied motor steps to allow proper tuning operations. This paper describes the electrical and mechanical performance of the cavity tuner during the commissioning and operation of the cryomodulus manufactured to date.
Download or read book Operating Experience with Superconducting Cavities at Jefferson Lab written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The CEBAF recirculating superconducting electron linac at Jefferson Lab is now in full operation supporting nuclear physics experiments in three target halls at up to 4.4 GeV. The 330 SRF cavities, operating at 2.0 K, continue to perform well above design specifications, and have accumulated over 8,000,000 operating cavity hours. The authors have to date no evidence of degradation of cavity performance. The SRF cavities have demonstrated excellent reliability. The one klystron per cavity design provides CEBAF with flexibility and redundancy for normal operations. Several techniques have been developed for establishing optimum operating conditions for the 330 independent systems. Operation of the cavities and control systems at the full design current of 1 mA has recently been achieved. The principal constraints on usable gradient for low current operations are (1) discharge at the cold ceramic rf window induced by electron field emission in cavities, (2) tuner controls, and (3) stability of the waveguide vacuum in the region between the warm and cold windows. Several cryomodules have been improved by application of rf helium processing while installed on the beamline.
Download or read book Superconducting Cavities from High Thermal Conductivity Niobium for CEBAF written by and published by . This book was released on 1991 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Continuous Electron Beam Accelerator Facility (CEBAF) is presently under construction in Newport News, VA. The accelerator consists of approximately 169 meters of 5-cell niobium cavities made from high thermal conductivity niobium with RRR values> 250. Cavities have been manufactured of material from three different suppliers. The material properties like thermal conductivity, residual resistivity and tensile behavior are compared. Results on the performance of these cavities in the presence of high rf fields are reported. Q(sub)0 values as high as 10^10 at 2 K and accelerating gradient of E> 14 MV/m have been achieved.
Download or read book Effect of Cavity Vacuum on Performance of Superconducting Niobium Cavities December 1995 written by Peter Kneisel and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analysis of Performance Limitations for Superconducting Cavities written by Jean R. Delayen and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Normal Mode Analysis of the CEBAF Accelerator Upgraded Superconducting Cavities written by Tommy Hiatt and published by . This book was released on 1999 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Performance of Production SRF Cavities for CEBAF written by and published by . This book was released on 1993 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Construction of the Continuous Electron Beam Accelerator Facility recirculating linac represents the largest scale application of superconducting rf (SRF) technology to date. Over 250 of the eventual 338 SRF 1497 MHz cavities have been assembled into hermetic pairs and completed rf testing at 2.0 K. Although the rf performance characteristics well exceed the CEBAF baseline requirements of Q[sub 0] = 2.4[times]10[sup 9] at 5 MV/m, the usual limiting phenomena are encountered field emission, quenching, Q-switching, will occasional multipacting. An analysis of the occurrence conditions and severity of these phenomena during production cavity testing is presented. The frequency with which performance is limited by quenching suggests that additional material advances may be required for applications which require the reliable achievement of accelerating gradients of more than 15 MV/m. The distributions of frequency and Q for a higher-order mode are also presented.
Download or read book Improvement of the Operational Performance of SRF Cavities Via in Situ Helium Processing and Waveguide Vacuum Processing written by and published by . This book was released on 1997 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The useful performance range of the superconducting rf (SRF) cavities in the CEBAF accelerator at Jefferson Lab is frequently limited by electron field emission and derived phenomena. Improvements are required to support future operation of the accelerator at higher than 5 GeV. Twelve operational cryomodules have been successfully processed to higher useful operating gradients via rf-helium processing. Progress against field emission was evidenced by improved high-field Q, reduced x-ray production and greatly reduced incidence of arcing at the cold ceramic window. There was no difficulty reestablishing beamline vacuum following the processing. Cavities previously limited to 4-6 MV/m are now operating stably at 6-9 MV/m. By applying a pulsed-rf processing technique, we have also improved the pressure stability of the thermal transition region of the input waveguide for several cavities.
Download or read book High Energy Accelerators Heacc 92 Proceedings Of The Xv International Conference In 2 Volumes written by J Rossbach and published by World Scientific. This book was released on 1993-02-10 with total page 1288 pages. Available in PDF, EPUB and Kindle. Book excerpt: The High Energy Accelerator Conference has always been the monitor of the state of the art and the new trends in planning, construction and operation of large particle accelerators. It is held every three years. The 1992 conference is devoted to High Energy Hadron Accelerators and Colliders, Linear Colliders, e⁺e⁻ Storage Rings and related Technologies for these machines. In addition to status reports and contributed papers, the program features twelve survey talks which include summaries of individual poster papers.
Download or read book Analysis of Mechanical Fabrication Experience with CEBAF s Production SRF Cavities written by and published by . This book was released on 1993 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: CEBAF has received a total of 360 five-cell niobium cavities, the largest group of industrially fabricated superconducting cavities so far. An extensive data base exists on the fabrication, surface treatment, assembly and cavity performance parameters. Analysis of the mechanical features of the cavities includes the following: the spread in fabrication tolerances of the cells derived from field profiles of the ''as fabricated'' cavities and the ''as fabricated'' external Q-values of the fundamental power coupler compared to dimensional deviations. A comparison is made of the pressure sensitivity of cavities made of materials from different manufacturers between 760 torr (4.2 K) and 23 torr (2 K).
Download or read book Cebaf SRF Performance During Initial 12 GeV Commissioning written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Continuous Electron Beam Accelerator Facility (CEBAF) energy upgrade from 6 GeV to 12 GeV includes the installation of eleven new 100 MV cryomodules (88 cavities). The superconducting RF cavities are designed to operate CW at an accelerating gradient of 19.3 MV/m with a QL of 3×107. Not all the cavities were operated at the minimum gradient of 19.3 MV/m with the beam. Though the initial 12 GeV milestones were achieved during the initial commissioning of CEBAF, there are still some issues to be addressed for long term reliable operation of these modules. This paper reports the operational experiences during the initial commissioning and the path forward to improve the performance of C100 (100 MV) modules.
Download or read book CEBAF written by and published by . This book was released on 1988 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Continuous Electron Beam Accelerator Facility (CEBAF) will be a 4-GeV, 200 micro-amp superconducting recirculating linear accelerator to provide CW electron beams to simultaneous nuclear physics experiments in three end stations. Funded by the Department of Energy, CEBAF's purpose is basic research on the nuclear many-body system, its matter. At the heart of the accelerator are niobium superconducting accelerator cavities designed at Cornell University and successfully prototyped with industry during the past three years. The cavities consistently exceed CEBAF's performance specifications (gradient> or = 5 MV/m, Q(sub)0> or = 2.4*10^9 at 2 K and 5 MV/m). Construction is under way, and operation is scheduled in 1994.
Download or read book Operation of the RF Controls in the CEBAF Injector written by and published by . This book was released on 1990 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The CEBAF injector has produced its first relativistic beam with two superconducting cavities. Six RF control modules are used to control amplitude and phase in the chopper cavities, the buncher, the capture section, and the two superconducting cavities. In this paper the required stability and actual performance of the modules are discussed. For the superconducting cavity control, performance is consistent with energy stability of ~ 10^-4.
