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RF Power Detector/Monitor Upgrade for the 500MHz Systems at the ALS

Description: Several systems rely on the accurate and linear detection of 500 MHz signals, (the fundamental frequency of both the Booster Ring and Storage Ring) over a dynamic range in excess of 25dB. Prior to this upgrade, the detector/monitor was diode based and though this type of detector could handle the dynamic range requirement it could not do so in an accurate and linear manner. In order to meet the requirements (dynamic range greater than or equal to 25dB, accurate and linear to +-0.25dB over the range, and additional circuitry to interface to the legacy control system and interlocks), a new RF Power Detector/Monitor has been developed using two AD8361, Analog Devices Tru RMS Detectors and a fuzzy comparator, which extends the overall detector's range to twice that of the AD8361. Further information is available [www.analogedevices.com/]. Details of the design requirements and the detector/monitor's circuit as well as the performance of the detector will be presented.
Date: May 8, 2003
Creator: Baptiste, K.
Partner: UNT Libraries Government Documents Department

Advanced light source storage ring rf system

Description: The short electron bunch length (30ps design target) of the Advanced Light Source (ALS) stored beam is capable exciting a wide spectrum of higher order mode (HOM) frequencies. Further, the small aperture and low cut off frequency of the beam enveloping components does not allow for transmission and consequent attenuation of the lower frequency HOM components. The small cross section and divergence of the high brightness electron beam will allow for more sophisticated high resolution experiments by synchrotron radiation users. A more stringent requirement on beam position stability results, however. In this area transmitted mechanical vibration becomes a problem. The ALS RF system splits 300kW of CW 500MHz power between two single cell cavities. Compared to past practice this power rating is high. The use of only two cavities however has some advantages, it simplifies the waveguide feed system and releases room in straight sections for insertion devices, more important it reduces HOM and beam impedance problems. 3 refs., 2 figs.
Date: March 1, 1989
Creator: Taylor, B.; Baptiste, K.; Lancaster, H. & Lo, C.C.
Partner: UNT Libraries Government Documents Department

The amplitude and phase control of the ALS Storage Ring RF System

Description: A 500MHz, 300KW Klystron power amplifier provides RF power to the ALS Storage Ring. In order to accommodate the amplitude and phase changes during beam stacking and decay, which demand continuously varying power levels from the Klystron, four loops are used to keep the system operating properly, with two of those loops dedicated to keeping the two cavity tuners on tune. Description of the control loops and their performance data will be given. Using the modulation anode of the Klystron in the amplitude loop will be discussed.
Date: March 1, 1995
Creator: Lo, C.C.; Taylor, B. & Baptiste, K.
Partner: UNT Libraries Government Documents Department

Advanced light source master oscillator

Description: The Master Oscillator of the Advanced Light Source operates at a frequency of 499.654 MHz which is the 328th harmonic of the storage ring. The oscillator is capable of providing up to a maximum of {plus minus} 500 KHz frequency deviation for various experimental purposes. Provisions for external signal injection as well as using an external signal source have been designed into the unit. A power distribution system has also been included to provide signals for various parts of the ALS machine and user requirements. The Master Oscillator is made up with modules housed in a Euro chassis. 4 refs., 7 figs.
Date: March 1, 1989
Creator: Lo, C.C.; Taylor, B. & Baptiste, K. (Lawrence Berkeley Lab., CA (USA))
Partner: UNT Libraries Government Documents Department

Third-harmonic RF cavity for the advanced light source

Description: It is proposed to upgrade the Advanced Light Source by the addition of an RF system at the third-harmonic (1.5 GHz), of the existing system. With the new system it will be possible to control the bunch length and charge density profile independently of the RF bucket height, improving the Touschek-dominated beam lifetime. A third-harmonic cavity design is described which has good efficiency and is relatively simple to manufacture. The cavity shape is presented and issues of shunt impedance, power dissipation, higher-order modes, fabrication and installation are discussed. Design options for the cavity tuner and RF window are also considered.
Date: July 1, 1998
Creator: Baptiste, K; Byrd, J; Franks, M; Henderson, T; Lo, C C; Plate, D et al.
Partner: UNT Libraries Government Documents Department

Hom dampers for ALS storage ring RF cavities

Description: The main source of narrowband impedance in the Advanced Light Source (ALS) are higher order modes (HOMs) of the two main RF and three third harmonic cavities. These HOMs drive longitudinal and transverse coupled bunch instabilities, which are controlled using active beam feedback systems. The dominant longitudinal HOMs in both systems are TM011-like modes with the R/Q factor an order of magnitude higher than all other longitudinal modes. To reduce the growth rates within the range of the longitudinal feedback system (LFB), these modes were tuned away from beam resonances by means of cooling water temperature control (main rf system), and the combination of two tuners (third harmonic system). To improve the reliability of the longitudinal dampening system, we have built and installed E-type HOM dampers for the fundamental and harmonic cavities. We present the design, commissioning and performance of the HOM dampers in this paper.
Date: May 8, 2003
Creator: Kwiatkowski, S.; Baptiste, K.; Byrd, J.; DeSantis, S.; Julian, J.; Low, R. et al.
Partner: UNT Libraries Government Documents Department

Design of a VHF-band RF Photoinjector with Megahertz BeamRepetition Rate

Description: New generation accelerator-based X-ray light sources require high quality beams with high average brightness. Normal conducting L- and S-band photoinjectors are limited in repetition rate and D-C (photo)injectors are limited in field strength at the cathode. We propose a low frequency normal-conducting cavity, operating at 50 to 100MHz CW, to provide beam bunches of up to the cavity frequency. The photoinjector uses a re-entrant cavity structure, requiring less than 100 kW CW, with a peak wall power density less than 10 W/cm{sup 2}. The cavity will support a vacuum down to 10 picoTorr, with a load-lock mechanism for easy replacement of photocathodes. The photocathode can be embedded in a magnetic field to provide correlations useful for emittance exchange. Beam dynamics simulations indicate that normalized emittances smaller than 1 mm-mrad are possible with gap voltage of 750 kV, with fields up to 20 MV/m at the photocathode, for 1 nanocoulomb charge per bunch after acceleration and emittance compensation. Long-bunch operation (10's of picosecond) is made possible by the low cavity frequency, permitting low bunch current at the 750 kV gap voltage.
Date: June 1, 2007
Creator: Staples, J.W.; Baptiste, K.M.; Corlett, J.N.; Kwiatkowski, S.; Lidia, S.M.; Qiang, J. et al.
Partner: UNT Libraries Government Documents Department

Design Studies for a VUV--Soft X-ray Free-Electron Laser Array

Description: Several recent reports have identified the scientific requirements for a future soft X-ray light source [1, 2, 3, 4, 5], and a high-repetition-rate free-electron laser (FEL) facility responsive to them is being studied at Lawrence Berkeley National Laboratory (LBNL) [6]. The facility is based on a continuous-wave (CW) superconducting linear accelerator with beam supplied by a high-brightness, high-repetition-rate photocathode electron gun operating in CW mode, and on an array of FELs to which the accelerated beam is distributed, each operating at high repetition rate and with even pulse spacing. Dependent on the experimental requirements, the individualFELs may be configured for either self-amplified spontaneous emission (SASE), seeded highgain harmonic generation (HGHG), echo-enabled harmonic generation (EEHG), or oscillator mode of operation, and will produce high peak and average brightness x-rays with a flexible pulse format ranging from sub-femtoseconds to hundreds of femtoseconds. This new light source would serve a broad community of scientists in many areas of research, similar to existing utilization of storage ring based light sources. To reduce technical risks and constructioncosts, accelerator research, development, and design studies at LBNL target the most critical components and systems of the facility. We are developing a high-repetition-rate low-emittance electron gun, high quantum efficiency photocathodes, and have embarked on design and optimization of the electron beam accelerator, FEL switchyard, and array of FELs. We continue our work on precision timing and synchronization systems critical for time-resolved experiments using pump-probe techniques.
Date: August 4, 2009
Creator: Corlett, J.; Baptiste, K.; Byrd, J.M.; Denes, P.; Falcone, R.; Kirz, J. et al.
Partner: UNT Libraries Government Documents Department

Recent Beam Measurements and New Instrumentation at the Advanced Light Source

Description: The Advanced Light Source (ALS) in Berkeley was the first of the soft x-ray third generation light source ever built, and since 1993 has been in continuous and successful operation serving a large community of users in the VUV and soft x-ray community. During these years the storage ring underwent through several important upgrades that allowed maintaining the performance of this veteran facility at the forefront. The ALS beam diagnostics and instrumentation have followed a similar path of innovation and upgrade and nowadays include most of the modem and last generation devices and technologies that are commercially available and used in the recently constructed third generation light sources. In this paper we will not focus on such already widely known systems, but we will concentrate our effort in the description of some measurements techniques, instrumentation and diagnostic systems specifically developed at the ALS and used during the last few years.
Date: April 11, 2012
Creator: Sannibale, F.; Baptiste, K.; Barry, W.; Chin, M.; /LBL, Berkeley; Filippetto, D. et al.
Partner: UNT Libraries Government Documents Department

Successful Completion of the Top-off Upgrade of the Advanced Light Source

Description: An upgrade of the Advanced Light Source to enable top-off operation has been completed during the last four years. The final work centered around radiation safety aspects, culminating in a systematic proof that top-off operation is equally safe as decaying beam operation. Commissioning and transition to full user operations happened in late 2008 and early 2009. Top-off operation at the ALS provides a very large increase in time-averaged brightness (by about a factor of 10) as well as improvements in beam stability. The following sections provide an overview of the radiation safety rationale, commissioning results, as well as experience in user operations.
Date: January 31, 2010
Creator: Steier, C.; Bailey, B.; Baptiste, K.; Barry, W.; Biocca, A.; Byrne, W. et al.
Partner: UNT Libraries Government Documents Department

A Next Generation Light Source Facility at LBNL

Description: The Next Generation Light Source (NGLS) is a design concept, under development at LBNL, for a multibeamline soft x-ray FEL array powered by a ~;;2 GeV superconducting linear accelerator, operating with a 1 MHz bunch repetition rate. The CW superconducting linear accelerator is supplied by a high-brightness, highrepetition- rate photocathode electron gun. Electron bunches are distributed from the linac to the array of independently configurable FEL beamlines with nominal bunch rates up to 100 kHz in each FEL, and with even pulse spacing. Individual FELs may be configured for EEHG, HGHG, SASE, or oscillator mode of operation, and will produce high peak and average brightness x-rays with a flexible pulse format, with pulse durations ranging from sub-femtoseconds to hundreds of femtoseconds.
Date: March 23, 2011
Creator: Corlett, J.N.; Austin, B.; Baptiste, K.M.; Byrd, J.M.; Denes, P.; Donahue, R. et al.
Partner: UNT Libraries Government Documents Department