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High-yield positron systems for linear colliders

Description: Linear colliders, such as the SLC, are among those accelerators for which a high-yield positron source operating at the repetition rate of the accelerator is desired. The SLC, having electron energies up to 50 GeV, presents the possibility of generating positron bunches with useful charge even exceeding that of the initial electron bunch. The exact positron yield to be obtained depends on the particular capture, transport and damping system employed. Using 31 GeV electrons impinging on a W-type converter phase-space at the target to the acceptance of the capture rf section, the SLC source is capable of producing, for every electron, up to two positrons within the acceptance of the positron damping ring. The design of this source and the performance of the positron system as built are described. Also, future prospects and limitations for high-yield positron systems are discussed. 11 refs., 5 figs., 3 tabs.
Date: April 1, 1989
Creator: Clendenin, J.E.
Partner: UNT Libraries Government Documents Department

Notes on the IMACON 500 streak camera system

Description: The notes provided are intended to supplement the instruction manual for the IMACON 500 streak camera system. The notes cover the streak analyzer, instructions for timing the streak camera, and calibration. (LEW)
Date: January 31, 1985
Creator: Clendenin, J.E.
Partner: UNT Libraries Government Documents Department

Summary of Polarized e-/e+ Source Presentations

Description: The development of polarized electron sources in the 1970s capable of generating beams for injection into electron accelerators has been a major enabling factor for spin physics with electrons during the past quarter century. These sources continue to be refined for higher polarization and better operability. Recent developments were presented at this workshop in both plenary sessions and in 2 separate parallel sessions. The ILC plans to utilize not only a polarized electron source but also a polarized positron source. The current state of two types of positron sources were presented. This paper is a brief summary of all of these presentations.
Date: November 28, 2007
Creator: Clendenin, J. E.
Partner: UNT Libraries Government Documents Department

Polarized electron sources

Description: Polarized electron sources for high energy accelerators took a significant step forward with the introduction of a new laser-driven photocathode source for the SLC in 1992. With an electron beam polarization of >80% and with {approximately}99% uptime during continuous operation, this source is a key factor in the success of the current SLC high-energy physics program. The SLC source performance is used to illustrate both the capabilities and the limitations of solid-state sources. The beam requirements for future colliders are similar to that of the SLC with the addition in most cases of multiple-bunch operation. A design for the next generation accelerator source that can improve the operational characteristics and at least minimize some of the inherent limitations of present sources is presented. Finally, the possibilities for producing highly polarized electron beams for high-duty-factor accelerators are discussed.
Date: May 1, 1995
Creator: Clendenin, J.E.
Partner: UNT Libraries Government Documents Department

Beam parametr measurements for the SLAC linear collider

Description: A stable, closely-controlled, high-intensity, single-bunch beam will be required for the SLAC Linear Collider. The characteristics of short-pulse, low-intensity beams in the SLAC linac have been studied. A new, high-intensity thermionic gun, subharmonic buncher and S-band buncher/accelerator section were installed recently at SLAC. With these components, up to 10/sup 11/ electrons in a single S-band bunch are available for injection into the linac. the first 100-m accelerator sector has been modified to allow control of short-pulse beams by a model-driven computer program. Additional instrumentation, including a computerized energy analyzer and emittance monitor have been added at the end of the 100-m sector. The beam intensity, energy spectrum, emittance, charge distribution and the effect of wake fields in the first accelerator sector have been measured. The new source and beam control system are described and the most recent results of the beam parameter measurements are discussed.
Date: January 1, 1981
Creator: Clendenin, J.E.; Blocker, C. & Breidenbach, M.
Partner: UNT Libraries Government Documents Department

RF photoinjectors

Description: RF photoinjectors have been under intensive development for the past decade since they promise to be the high-brightness electron beam sources required for FELs. Progress has been sufficiently good to make optically switched RF photoinjectors attractive candidates as injectors for future colliders, especially those colliders which plan to use complex beam pulse structures. Although present RF photoinjectors will not today meet all the requirements of some collider designs, their potential capabilities seem greater as well as more versatile than conventional injectors. The present status and future goals of RF photoinjectors are compared. The principal problems remaining for achieving these goals while also providing high reliability for linacs during continuous, long-term operation are examined.
Date: August 1, 1996
Creator: Clendenin, J.E.
Partner: UNT Libraries Government Documents Department

The high-gradient S-band linac for initial acceleration of the SLC (SLAC linear collider) intense positron bunch

Description: Although short lengths of S-band standing-wave, disk-loaded waveguide have been successfully RF-processed to accelerating gradients equivalent to about 175 MeV/m in a traveling-wave structure, the 20 MeV/m gradient of the SLC 50 GeV linac has been the highest gradient S-band accelerator in operation. However, the 1.5 m traveling-wave constant impedance capture section for the SLC positron source, operating with a dedicated 60 MW klystron, is now routinely accelerating single-bunch beams of more than 7 /times/ 10/sup 10/ e/sup +//pulse at rates of up to 60 Hz with an accelerating gradient section are described. 11 refs., 1 fig. 1 tab.
Date: August 1, 1989
Creator: Clendenin, J.E.; Ecklund, S.D. & Hoag, H.A.
Partner: UNT Libraries Government Documents Department

Timing jitter measurements at the SLC electron source

Description: The SLC thermionic gun and electron source produce a beam of up to 15 /times/ 10/sup 10/ /sub e//minus/ in a single S-band bunch. A 170 keV, 2 ns FWHM pulse out of the gun is compressed by means of two subharmonic buncher cavities followed by an S-band buncher and a standard SLAC accelerating section. Ceramic gaps in the beam pipe at the output of the gun allow a measure of the beam intensity and timing. A measurement at these gaps of the timing jitter, with a resolution of <10 ps, is described. 3 refs., 5 figs.
Date: March 1, 1989
Creator: Sodja, J.; Browne, M.J. & Clendenin, J.E.
Partner: UNT Libraries Government Documents Department

Solid state high power amplifier for driving the SLC injector klystron

Description: The SLC injector klystron rf drive is now provided by a recently developed solid-state amplifier. The high gain of the amplifier permits the use of a fast low-power electronic phase shifter. Thus the SLC computer control system can be used to shift the phase of the high-power rf rapidly during the fill time of the injector accelerator section. These rapid phase shifts are used to introduce a phase-energy relationship in the accelerated electron pulse in conjunction with the operation of the injector bunch compressor. The amplifier, the method of controlling the rf phase, and the operational characteristics of the system are described. 5 refs., 4 figs.
Date: March 1, 1985
Creator: Judkins, J.G.; Clendenin, J.E. & Schwarz, H.D.
Partner: UNT Libraries Government Documents Department

The SLC polarized electron source

Description: A polarized electron source consisting of a 3-electrode photocathode gun and a flashlamp-pumped dye laser has been designed and built for the SLC and is currently undergoing commissioning. The source is described, and the operating configuration is discussed. The present status of the source and future plans are briefly indicated. 7 refs., 4 figs.
Date: October 1, 1990
Creator: Clendenin, J. E.
Partner: UNT Libraries Government Documents Department

Polarized electronic sources for future e{sup +}/e{sup {minus}} linear colliders

Description: Polarized electron beams will play a crucial role in maximizing the physics potential for future e{sup +}/e{sup {minus}} linear colliders. We will review the SLC polarized electron source (PES), present a design for a conventional PES for the Next Linear Collider (NLC), and discuss the physics issues of a polarized RF gun.
Date: May 1, 1997
Creator: Tang, H.; Alley, R.K. & Clendenin, J.E.
Partner: UNT Libraries Government Documents Department

Real time bunch length measurements in the SLC linac

Description: The longitudinal charge distribution of bunches accelerated in the Stanford Linear Collider (SLC) linac will strongly affect the performance of the Collider. Bunch lengths are chosen in a balance between the deleterious effects of longitudinal and transverse wakefields. The former impacts on the beam energy spread whereas the latter is important to the transverse emittance. Two bunch length measurement ports have been installed in the SLC linac: one in the injector region and one after the emittance damping ring to linac reinjection point. These ports utilize a fused quartz Cerenkov radiator in conjunction with an electrooptic streak camera to permit real time monitoring of single s-band buckets with a resolution of several picoseconds. The design of the radiators and light collection optics is discussed with an emphasis on those issues important to high resolution. Experimental results are presented. 7 refs., 4 figs.
Date: February 1, 1985
Creator: Sheppard, J.C.; Clendenin, J.E.; James, M.B.; Miller, R.H. & Ross, M.C.
Partner: UNT Libraries Government Documents Department

Single-bunch beams for BC-75

Description: On June 8, 1983, a beam consisting of a single S-band bunch was transported through the linac into the beam switchyard (BSY) and analyzed in the C-line (Beamline 27) at 30 GeV. The C-line toroid 2712 measured an intensity of approximately 2 x 10/sup 9/e/sup -//pulse. The exact intensity was uncertain due to the limited response time of the toroid for fast, single-bunch beams. However, the linear Q intensity monitors (Lin Q) showed the transmission of the beam through the linac between Sectors 2 and 30 to be fairly flat with an intensity of 3 x 10/sup 9/e/sup -//pulse in the final 19 sectors. The CID Faraday cup, which is located adjacent to the Gun Lin Q, was used to check the calibration of the Lin Q.
Date: June 1, 1983
Creator: Sodja, J.; Clendenin, J.E.; Erickson, R.A. & Miller, R.H.
Partner: UNT Libraries Government Documents Department

Nonintercepting emittance monitor

Description: A nonintercepting emittance monitor is a helpful device for measuring and improving particle beams in accelerators and storage rings as it allows continuous monitoring of the beam's distribution in phase space, and perhaps closed loop computer control of the distributions. Stripline position monitors are being investigated for use as nonintercepting emittance monitors for a beam focused by a FODO array in the first 100 meters of our linear accelerator. The technique described here uses the signal from the four stripline probes of a single position monitor to measure the quadrupole mode of the wall current in the beam pipe. This current is a function of the quadrupole moment of the beam, sigma/sup 2//sub x/ - sigma/sup 2//sub y/. In general, six independent measurements of the quadrupole moment are necessary to determine the beam emittance. This technique is dependent on the characteristically large variations of sigma/sup 2//sub x/ - sigma/sup 2//sub y/ in a FODO array. It will not work in a focusing system where the beam is round at each focusing element.
Date: August 1, 1983
Creator: Miller, R.H.; Clendenin, J.E.; James, M.B. & Sheppard, J.C.
Partner: UNT Libraries Government Documents Department

Energy matching of 1. 2 GeV positron beam to the SLC (Stanford Linear Collider) damping ring

Description: Positrons collected at the SLC positron source are transported over a 2-km path at 220 MeV to be reinjected into the linac for acceleration to 1.2 GeV, the energy of the emittance damping ring. Since the positron bunch length is a significant fraction of a cycle of the linac-accelerating RF, the energy spread at 1.2 GeV is considerably larger than the acceptance of the linac-to-ring (LTR) transport system. Making use of the large pathlength difference at the beginning of the LTR due to this energy spread, a standard SLAC 3-m accelerating section has been installed in the LTR to match the longitudinal phase space of the positron beam to the acceptance of the damping ring. The design of the matching system is described, and a comparison of operating results within simulations is presented. 5 refs., 4 figs., 1 tab.
Date: August 1, 1989
Creator: Clendenin, J.E.; Helm, R.H.; Jobe, R.K.; Kulikov, A. & Sheppard, J.C.
Partner: UNT Libraries Government Documents Department

Timing stabilization for the SLC electron source

Description: The timing stability required for the SLC electron source is determined by the energy acceptance of the electron damping ring. The jitter requirements for the gun pulse itself are somewhat mitigated by the subsequent bunching process. The desogn of the system by which a gun pulse stability of sigma approx. 20 ps is achieved is described, and experiments to measure the resulting energy stability under various bunching conditions are discussed.
Date: February 1, 1987
Creator: Clendenin, J.E.; Browne, M.J.; Gearhart, R.A.; Sheppard, J.C. & Sodja, J.
Partner: UNT Libraries Government Documents Department

Single bunch beam measurements for the proposed SLAC linear collider

Description: Single S-band bunches of approx. 10/sup 9/ electrons have been used to study the characteristics of the SLAC linac in anticipation of its operation as a linear collider. Emittance measurements have been made, the longitudinal charge distribution within single bunches has been determined and transverse emittance growth has been produced by deliberately missteering the beam. New equipment is being installed and checked out, and the sensitivity of new traveling-wave beam position monitors has been measured.
Date: February 1, 1981
Creator: Clendenin, J.E.; Loew, G.A.; Miller, R.H.; Pellegrin, J.L. & Truher, J.B.
Partner: UNT Libraries Government Documents Department

Performance of the SLC polarized electron source with high polarization

Description: For the 1992 operating cycle of the SLAC Linear Collider (SLC), the polarized electron source (PES) during its maiden run successfully met the pulse intensity and overall efficiency requirements of the SLC. However, the polarization of the bulk GaAs cathode was low ({approximately}27%) and the pulse-to-pulse stability was marginal. We have shown that adequate charge for the SLC can be extracted from a strained layer cathode having P{sub e}{approximately}80% even though the quantum efficiency (QE) is < 1%. The recent addition of a separate chamber to the PES-which allows cathodes to be loaded into the gun after the vacuum bake and after high voltage (HV) processing without breaking vacuum-increases the reliability for achieving an adequate photoelectron yield. A new SLAC-built pulsed Ti:sapphire laser permits operation of the PES at the required wavelength with sufficient power to fully saturate the yield, and thus improve the e{sup {minus}} beam stability. The performance of the PES during the 1993 SLC operating cycle with these and other improvements is discussed.
Date: April 1, 1993
Creator: Clendenin, J. E.; Alley, R. K. & Aoyagi, H.
Partner: UNT Libraries Government Documents Department

Performance of the SLC polarized electron source and injector with the SLAC 3 km linac configured for fixed target experiments

Description: The SLC polarized electron source (PES) can be modified to produce {mu}sec-long pulses for injection into the un-SLEDed SLAC 3 km linac, with a duty factor considerably higher than for SLC. Such beams are desirable for fixed target experiments at SLAC requiring polarized electron beams of up to 50 mA within an energy spread of 0.5%, at energies of up to 26 GeV. During the fall of 1992, the SLAC linac was operated continuously for two months unSLEDed with the PES dye laser (715 nm) modified to produce a 1{mu}ec pulse at 120Hz. An AlGaAs photocathode was installed in the electron gun to achieve 40% polarization, and a prebuncher was added to the SLC injector to improve capture for long pulse beams. We discuss the performance eo the polarized electron beam for long pulse operation.
Date: March 1, 1993
Creator: Yeremian, A. D.; Alley, R. K. & Clendenin, J. E.
Partner: UNT Libraries Government Documents Department

RF Gun Photo-Emission Model for Metal Cathodes Including Time Dependent Emission

Description: The quantum efficiency from a metal cathode is strongly dependent on the field at the cathode due to the Schottky effect. Since the field is time dependent the quantum efficiency is also time dependent. Thus the laser pulse shape used to generate electrons in a photocathode rf gun is not the same as the electron bunch shape. In addition since the thermal emittance and quantum efficiency are related, the thermal emittance is also time dependent.
Date: February 24, 2006
Creator: Schmerge, J.F.; Clendenin, J.E.; Dowell, D.H.; Gierman, S.M. & /SLAC
Partner: UNT Libraries Government Documents Department

Emittance calculations for the Stanford Linear Collider injector

Description: A series of measurements have been performed to determine the emittance of the high intensity, single bunch beam that is to be injected into the Stanford Linear Collider. On-line computer programs were used to control the Linac for the purpose of data acquisition and to fit the data to a model in order to deduce the beam emittance. This paper will describe the method of emittance calculation and present some of the measurement results.
Date: March 1, 1983
Creator: Sheppard, J.C.; Clendenin, J.E.; Helm, R.H.; Lee, M.J.; Miller, R.H. & Blocker, C.A.
Partner: UNT Libraries Government Documents Department

Isochronous 180 degree turns for the SLC positron system

Description: The design of the compact, achromatic, second order isochronous 180{degrees} turn for the SLC positron transport system will be described. Design criteria require an energy range of 200{plus minus}20 MeV, energy acceptance of {plus minus}5%, transverse admittance of 25{pi} mm-mr, and minimal lengthening of the 3 to 4 mm (rms) positron bunch. The devices had to fit within a maximum height or width of about 10 ft. Optics specifications and theoretical performance are presented and compared to experimental results based on streak camera measurements of bunch length immediately after the first isochronous turn (200 MeV) and positron beam energy spread after S-band acceleration to 1.15 GeV. 5 refs., 7 figs.
Date: May 1, 1991
Creator: Helm, R.H.; Clendenin, J.E.; Ecklund, S.D.; Kulikov, A.V. & Pitthan, R.
Partner: UNT Libraries Government Documents Department

Update on the high-current injector for the Stanford Linear collider

Description: The high current injector has become operational. There are two crucial areas where improvements must be made to meet collider specifications: while the injector can produce up to 10/sup 11/ e/sup -/ in a single S-band bucket, initially much of this charge was captured in a low energy tail and was this not suitable for transport through the accelerator and injection into the damping ring. Pulse to pulse position jitter has been observed, resulting in transverse wake field which increases beam emittance. The problems described above contribute to substantial current loss during transport from the injector (40 MeV) to the SLC damping ring (1.2 GeV). Experimental studies are continuing with the aim of understanding and improving beam characteristics including bunch length, pulse to pulse stability and emittance. The present status of these studies is reported.
Date: March 1, 1983
Creator: James, M.B.; Clendenin, J.E.; Ecklund, S.D.; Miller, R.H.; Sheppard, J.C.; Sinclair, C.K. et al.
Partner: UNT Libraries Government Documents Department

Multi-channel pulser for the SLC thermionic electron source

Description: A new pulser developed for the SLC thermionic gun has been operational since September 1984. It consists of two planar triode amplifiers with a common output triode driving the gun cathode to produce two independent pulses of up to 9A with a 3 nsec FWHM pulse width. Three long-pulse amplifiers are also connected to the cathode to produce pulses with widths controllable between 100 nsec and 1.6 ..mu..sec. Each amplifier has independent timing and amplitude control through a fiber optic link to the high voltage plane of the gun cathode-grid structure. The pulser and its operating characteristics are described. 15 refs., 3 figs.
Date: January 1, 1985
Creator: Browne, M.J.; Clendenin, J.E.; Corredoura, P.L.; Jobe, R.K.; Koontz, R.F. & Sodja, J.
Partner: UNT Libraries Government Documents Department