The coax based MO distribution system in the ALS is going to be replaced by a modernized, lower phase noise and more interference tolerant version, ready to support ALS-U operation. System aspects are shown and several commercial analog... more
The coax based MO distribution system in the ALS is going to be replaced by a modernized, lower phase noise and more interference tolerant version, ready to support ALS-U operation. System aspects are shown and several commercial analog and digital optical transceiver modules are compared for their suitability in this application. Furthermore, recent phase noise optimizing efforts in the ALS RF system are discussed and several prototypes for a custom built, low phase noise, frequency adjustable master oscillator around 500 MHz are shown.
Research Interests:
A multi-objective genetic algorithm-based optimization process has been applied to optimize the RF design of a 500 MHz main cavity and a 1.5 GHz Higher Harmonic Cavity (HHC) for the Advanced Light Source upgrade (ALS-U) in Lawrence... more
A multi-objective genetic algorithm-based optimization process has been applied to optimize the RF design of a 500 MHz main cavity and a 1.5 GHz Higher Harmonic Cavity (HHC) for the Advanced Light Source upgrade (ALS-U) in Lawrence Berkeley National Laboratory (LBNL). For the main cavity, a significant improvement, compared with the existing ALS cavity, has been achieved in cavity shunt impedance and power loss density simultaneously. The field strengths and distribution of the optimized structure are analysed for further research. For the HHC, a cavity with low R/Q has been preliminary designed to mitigate the beam instability. This study also serves as an example of how a genetic algorithm can be used for optimizing RF cavities.
Research Interests:
The design of a 1.3 GHz buncher cavity for the APEX project, a MHz repetition rate high-brightness photoinjector, is presented. The buncher cavity operates at 240 kV in CW mode, and it compresses the 750 keV beam from APEX gun through... more
The design of a 1.3 GHz buncher cavity for the APEX project, a MHz repetition rate high-brightness photoinjector, is presented. The buncher cavity operates at 240 kV in CW mode, and it compresses the 750 keV beam from APEX gun through ballistic compression. Compared with a single cell design, a two-cell cavity doubles the shunt impedance to 7.8 M� , which greatly relaxes the requirements for both RF amplifier and cavity cooling. Coupler design, multipacting analysis, HOM analysis and thermal analysis will be presented in this paper.
Research Interests:
Science needs are pushing the development of MHz-class repetition-rate linac-based facilities generating high-brightness electron beams. The successful lower repetition-rate RF gun schemes cannot be scaled up to MHz rates. At LBNL, we... more
Science needs are pushing the development of MHz-class repetition-rate linac-based facilities generating high-brightness electron beams. The successful lower repetition-rate RF gun schemes cannot be scaled up to MHz rates. At LBNL, we developed the VHF-Gun, a room-temperature RF gun designed for CW operation and high-brightness beam performance.
Research Interests:
The ALS storage ring 500 MHz RF system uses two re-entrant accelerating cavities powered by a single 320kW PHILLIPS YK1305 klystron. During several years of initial operation, the RF cavities were not equipped with effective passive HOM... more
The ALS storage ring 500 MHz RF system uses two re-entrant accelerating cavities powered by a single 320kW PHILLIPS YK1305 klystron. During several years of initial operation, the RF cavities were not equipped with effective passive HOM damper systems. Longitudinal beam stability was achieved through cavity temperature control and the longitudinal feedback system (LFB), which was often operating at the
Research Interests:
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 25 dB. Prior to this upgrade, the detector/monitor was... more
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 25 dB. 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
Research Interests:
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... more
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
Research Interests:
RF cavities are essential components in particle accelerators not only for beam acceleration, but also for control purposes (bunch lengthening/shortening, deflecting and crabbing, transverse and longitudinal kickers) and for beam... more
RF cavities are essential components in particle accelerators not only for beam acceleration, but also for control purposes (bunch lengthening/shortening, deflecting and crabbing, transverse and longitudinal kickers) and for beam diagnostics (BPM). Normally, only a single resonating mode is actively used, although other modes can be excited by the circulating beam. Cavities used as longitudinal kickers for bunch-by-bunch feedback systems are designed with an axial mode, which, appropriately excited, provides a kick to the circulating bunches for maintaining beam stability. To provide the necessary bandwidth this mode has to be strongly damped resulting in quality factors of just a few units. In the longitudinal feedback kicker cavity just installed on the ALS we have detected a second axial mode which, although a few hundreds of MHz below the 1.4 GHz design mode, is also strongly damped and has a shunt impedance high enough to be appreciably excited by the feedback amplifier couplin...
Research Interests: Engineering and Physics
The APEX project at the Lawrence Berkeley National Laboratory is devoted to the development of a high repetition rate (MHz-class) electron injector for X-ray FEL applications. The injector is based on a new concept photo-gun, utilizing a... more
The APEX project at the Lawrence Berkeley National Laboratory is devoted to the development of a high repetition rate (MHz-class) electron injector for X-ray FEL applications. The injector is based on a new concept photo-gun, utilizing a normal conducting 186 MHz (VHF) RF cavity operating in CW mode in conjunction with high quantum efficiency photo-cathodes able to deliver the required repetition rates with available laser technology. The APEX activities are staged in phases. In Phases 0 and I, the electron photo-gun is constructed, tested and several different photo-cathodes, such as multialkali antimonides, cesium telluride [1], and diamond amplifiers [2], are tested at full repetition rate. In Phase II, a pulsed linac is added for accelerating the beam at several tens of MeV to prove the high brightness performance of the gun when integrated in an injector scheme. APEX is located in an existing area with a radiation shielding configuration limiting the repetition rate at Phase II...
Research Interests:
Research Interests:
The ALS upgrade to a diffraction-limited light source (ALS-U) depends on the ability to lengthen the stored bunches to limit the emittance growth and increase the beam life time. In order to achieve lengthening in excess of fourfold... more
The ALS upgrade to a diffraction-limited light source (ALS-U) depends on the ability to lengthen the stored bunches to limit the emittance growth and increase the beam life time. In order to achieve lengthening in excess of fourfold necessary to this end, we are investigating the use of the same passive 1.5 GHz normal-conducting RF cavities currently used on the ALS. While the upgraded ring RF parameters and fill pattern make it easier as long as the beaminduced phase transient is concerned, the large lengthening factor and the strongly non-linear lattice require particular attention to the cavities contribution to the machine overall impedance budget. In this paper we present our estimates of the narrow-band impedance obtained by numerical simulation and bench measurements of the cavities’ resonant modes.
The recent energy crisis in California has led us to investigate the high power RF systems at the Advanced Light Source (ALS) in order to decrease the energy consumption and power costs. We found the Storage Ring Klystron Power Amplifier... more
The recent energy crisis in California has led us to investigate the high power RF systems at the Advanced Light Source (ALS) in order to decrease the energy consumption and power costs. We found the Storage Ring Klystron Power Amplifier system operating as designed but with significant power waste. A simple proportional-integrator (PI) analog loop, which controls the klystron collector beam current, as a function of the output RF power, has been designed and installed. The design considerations, besides efficiency improvement, were to interface to the existing system without major expense. They were to also avoid the klystron cathode power supply filter's resonance in the loop's dynamics, and prevent a conflict with the existing Cavity RF Amplitude Loop dynamics. This efficiency loop will allow us to save up to 700 MW-hours of electrical energy per year and increase the lifetime of the klystron.
Research Interests:
The upgrade of the Advanced Light Source to enable top-off operation has been ongoing for the last four years. Activities over the last year have centered around radiation safety aspects, culminating in a systematic proof that top-off... more
The upgrade of the Advanced Light Source to enable top-off operation has been ongoing for the last four years. Activities over the last year have centered around radiation safety aspects, culminating in a systematic proof that top-off operation is equally safe as decaying beam operation, followed by commissioning and full user operations. Top-off operation at the ALS provides a very large increase in time-averaged brightness to ALS users (by about a factor of 10) as well as improvements in beam stability. The presentation will provide an overview of the radiation safety rationale, commissioning results, as well as experience in user operations.
Research Interests:
A higher harmonic cavity system is under construction in the ALS to extend beam lifetime. The implementation will be carried out in stages. The plan is to operate the system in the passive mode as a start and, depending on various... more
A higher harmonic cavity system is under construction in the ALS to extend beam lifetime. The implementation will be carried out in stages. The plan is to operate the system in the passive mode as a start and, depending on various factors, the plan may evolve into an active system eventually to attain the optimum beam lifetime at all beam current levels. The RF system must be designed accordingly to support the various stages of implementation. This report will describe the various RF systems along the path leading to the fully implemented system.
Research Interests:
The commissioning at the Lawrence Berkeley National Laboratory (LBNL) of a high-brightness high-repetition rate (MHz-class) photo-gun, based on a normal conducting 186 MHz (VHF-band) RF cavity operating in CW mode, is now completed. The... more
The commissioning at the Lawrence Berkeley National Laboratory (LBNL) of a high-brightness high-repetition rate (MHz-class) photo-gun, based on a normal conducting 186 MHz (VHF-band) RF cavity operating in CW mode, is now completed. The gun has been designed to satisfy the requirements for operating high-repetition rate 4th generation light sources. Test of high quantum efficiency photocathodes with bunches of hundreds pC at MHz repetition rate are now underway. They include, Cs2Te cathodes developed in collaboration with INFNLASA and multialkali antimonides (CsK2Sb), prepared by a collaborating group at LBNL. The present experimental results and the plan for future activities are presented.
Research Interests: Engineering and Physics
ALS is the 1.9GeV third generation synchrotron light source which has been operating since 1993 at Berkeley National Lab. The new RF system, which is now under construction will use two TH 2161B 300kW klystrons to power two single cell RF... more
ALS is the 1.9GeV third generation synchrotron light source which has been operating since 1993 at Berkeley National Lab. The new RF system, which is now under construction will use two TH 2161B 300kW klystrons to power two single cell RF cavities. In the new design the existing conventional crow-bar klystron protection system will be replaced with the fast disconnect switch. The switch consist of a 24 high voltage IGBT’s connected in series, equipped with static and dynamic balancing systems. The main advantage of using this new technology is faster action and virtually no stress for the components of the high voltage power supply. This paper will show the final lay-out and the test results of the production unit.
Research Interests:
The ALS-U project to upgrade the Advanced Light Source to a multi bend achromat lattice received CD-1 approval in 2018 marking the end of its conceptual design phase. The ALS-U design promises to deliver diffraction limited performance in... more
The ALS-U project to upgrade the Advanced Light Source to a multi bend achromat lattice received CD-1 approval in 2018 marking the end of its conceptual design phase. The ALS-U design promises to deliver diffraction limited performance in the soft x-ray range by lowering the horizontal emittance to about 70 pm rad resulting in two orders of magnitude brightness increase for soft x-rays compared to the current ALS. The design utilizes a nine bend achromat lattice, with reverse bending magnets and on-axis swap-out injection utilizing an accumulator ring. This paper presents recent design progress of the accelerator, as well as new results of the R&D program.
ALS is the 1.9GeV third generation synchrotron light source which has been operating since 1993 at Berkeley National Lab. Our team is now working on the design of a new RF power source (replacement of the existing 320kW klystron with 4... more
ALS is the 1.9GeV third generation synchrotron light source which has been operating since 1993 at Berkeley National Lab. Our team is now working on the design of a new RF power source (replacement of the existing 320kW klystron with 4 IOT’s). In the new design the existing conventional crow-bar klystron protection system will be replaced with a fast disconnect switch. The switch will be constructed out of 16 high-voltage IGBT’s connected in series equipped with static and dynamic balancing system. The main advantage of using this new technology is faster action and virtually no stress for the components of the high voltage power supply. This paper will describe the hardware design process and the test results of the prototype switch unit.
The Advanced Photo-cathode EXperiment (APEX) is an ongoing experiment of a high repetition rate low emittance VHF band gun (1). A low level RF (LLRF) control and monitoring subsystem is developed based on 5 LLRF4 (2) boards. One of them... more
The Advanced Photo-cathode EXperiment (APEX) is an ongoing experiment of a high repetition rate low emittance VHF band gun (1). A low level RF (LLRF) control and monitoring subsystem is developed based on 5 LLRF4 (2) boards. One of them is used for low level RF control and the other 4 are used as interlocks and RF monitors at differ- ent points of the system. The synchronization of the pho- tocathode laser is also controlled relative to the RF system. This paper summarizes the control algorithms implemented in the system firmware. cavity, and provide a user interface to monitor and control the system. Currently, the cavity frequency tuner has not been installed yet, so the RF drive frequency must be ad- justed to follow changes in the cavity resonance frequency. The LLRF system for APEX consists of one RF con- trol chassis and two monitor and interlock chassis. The RF control chassis drives a solid state amplifier followed by a 60 kW tetrodes to feed the cavity, and it also phase lo...
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 detectorlmonitor was... more
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 detectorlmonitor was diode based and though this trpe 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 t0.25dB over the range, and additional circuitry to interface to the legacy control system and interlocks) a new RF Power DetectorlMonitor has been developed using two AD8361, Analog Devices TNRMS Detectors and a fuzzy comparator, which extends the overall detector's range to twice that of the AD8361. Further information is available [www.analogedevices.coml]. Details of the design requirements and the detectorlmonitor's circuit as well as the performance of the detector will be presented.
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... more
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.
Research Interests:
ALS is one of the first third generation synchrotron light sources which has been operating since 1992 at Berkeley Lab. Presently, the ALS Storage Ring System is comprised of a single 330kW klystron feeding two normal-conducting... more
ALS is one of the first third generation synchrotron light sources which has been operating since 1992 at Berkeley Lab. Presently, the ALS Storage Ring System is comprised of a single 330kW klystron feeding two normal-conducting single-cell RF cavities via a WR1800 circulator and magic-tee transmission system. The klystron has operated well beyond its expected lifetime and even though replacement klystrons are available from a different manufacturer, we have opted to build the replacement amplifier with a system of four Inductive Output Tubes, (IOT). The new amplifier system will use Cavity Combiners (CaCo) to combine IOT outputs and a magic-tee to combine IOT pairs to feed the existing transmission line connected to the cavities. The existing HVPS will be upgraded to interface with the four IOT amplifiers and its crowbar will be replaced with a series solid-state switch. The system is being designed to operate with the industry standard external cavity IOTs (80kW) and integral cavi...
Recent reports have identified the scientific requirements for a future soft x-ray light source and a high-repetition-rate FEL facility responsive to them is being studied at LBNL: the Next Generation Light Source (NGLS). The facility is... more
Recent reports have identified the scientific requirements for a future soft x-ray light source and a high-repetition-rate FEL facility responsive to them is being studied at LBNL: the Next Generation Light Source (NGLS). The facility is based on a CW superconducting linear accelerator with beam supplied by a highbrightness, high-repetition-rate photocathode electron gun, and on an array of FELs to which the beam is distributed, each operating at high repetition rate and with even pulse spacing. Dependent on the experimental requirements, the individual FELs may be configured for either SASE, HGHG, 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. We are developing a design concept for a 10 beamline, coherent, soft x ray FEL array powered by a 2.4 GeV superconducting accelerator operating with a 1 MHz bunch repetition rate. Electron bunches are fanned...
Higher harmonic cavities (HHCs), also known as Landau cavities, have been proposed to increase the beam lifetime and Landau damping by lengthening the bunch and increasing the synchrotron tune spread. Here, we present an optimized 1.5 GHz... more
Higher harmonic cavities (HHCs), also known as Landau cavities, have been proposed to increase the beam lifetime and Landau damping by lengthening the bunch and increasing the synchrotron tune spread. Here, we present an optimized 1.5 GHz normal conducting HHC design for the Advanced Light Source Upgrade project at Lawrence Berkeley National Lab with a superconducting-like geometry for lower R/Q. The optimization goal is to reach the required shunt impedance while maintaining a relatively high Q value of the cavities. A multi-objective genetic algorithm (MOGA)-based optimization process is applied to optimize the radio frequency (RF) design. This study serves as an example of how a genetic algorithm can be used to optimize RF cavities. Detailed exploration and characterization of the MOGA-based RF cavity optimization have been demonstrated from the aspects of minimizing the coupled bunch instabilities and analyzing the higher-order modes and the corresponding impedance of the HHC.
Research Interests:
The ALS-U upgrade promises to deliver diffraction limited performance throughout the soft x-ray range by lowering the horizontal emittance to about 50 pm resulting in 2-3 orders of brightness increase for soft x-rays compared to the... more
The ALS-U upgrade promises to deliver diffraction limited performance throughout the soft x-ray range by lowering the horizontal emittance to about 50 pm resulting in 2-3 orders of brightness increase for soft x-rays compared to the current ALS. The design utilizes a multi bend achromat lattice with on-axis swap-out injection and an accumulator ring. One central design goal is to install and commission ALS-U within a short dark period. This paper summarizes the status of the conceptual design of the accelerator, as well as some results of the R&D program that has been ongoing for the last 3 years.
Research Interests:
Research Interests:
The ALS (Advanced Light Source) RF system splits 300 kW of CW 500-MHz 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... more
The ALS (Advanced Light Source) RF system splits 300 kW of CW 500-MHz 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 importantly, it reduces higher-order-mode and beam
Research Interests:
A 500 MHz, 300 kW 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... more
A 500 MHz, 300 kW 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
Research Interests:
Page 1. ADVANC???D LIGHl SOURCE MASl???R OSCILLATOR CC Lo, B. Taylor and K.Baptiste Lawrence Berkeley Laboratory University of California Berkeley, California 54720 USA ... There are two independent crystal oscil-lators in the system. ...
Research Interests:
The quality of infrared microscopy and spectroscopy data collected at synchrotron based sources is strongly dependent on noise. We have successfully identified and suppressed several noise sources affecting Beamline 1.4.3 at the Advanced... more
The quality of infrared microscopy and spectroscopy data collected at synchrotron based sources is strongly dependent on noise. We have successfully identified and suppressed several noise sources affecting Beamline 1.4.3 at the Advanced Light Source (ALS), resulting in significant reductions to the noise in the users' FTIR spectra. In this paper, we present our methods of noise source analysis and
Research Interests:
Research Interests:
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... more
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.
Research Interests:
Research Interests:
A high-brightness high-repetition rate photo-injector based on a normal conducting 187 MHz RF cavity design capable of CW operation is under construction at the Lawrence Berkeley National Laboratory. A field at the cathode of ~ 20 MV/m... more
A high-brightness high-repetition rate photo-injector based on a normal conducting 187 MHz RF cavity design capable of CW operation is under construction at the Lawrence Berkeley National Laboratory. A field at the cathode of ~ 20 MV/m accelerates electron bunches to 750 keV with peak current, energy spread and transverse emittance suitable for FEL and ERL applications. A vacuum load-lock mechanism is included and a 10 picoTorr range vacuum capability allows most types of high quantum efficiency photo-cathodes to operate at a MHz repetition rate with present laser technology. The status of the project is presented.
Research Interests:
Research Interests:
Typically storage ring light sources operate with the maximum number of bunches as possible with a gap for ion clearing. The Advanced Light Source (ALS) has 2 nanoseconds between bunches and typically operates with 276 bunches out of a... more
Typically storage ring light sources operate with the maximum number of bunches as possible with a gap for ion clearing. The Advanced Light Source (ALS) has 2 nanoseconds between bunches and typically operates with 276 bunches out of a possible 328. For experimenters doing timing experiment this bunch separation is too small and would prefer to see only one or
Research Interests:
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... more
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 ...
Research Interests:
ALS is a 1.9 GeV third generation synchrotron light source that has been operating since 1992 at Lawrence Berkeley National Laboratory. There are two typical modes of operation of the ALS storage ring. In multibunch mode, the ring is... more
ALS is a 1.9 GeV third generation synchrotron light source that has been operating since 1992 at Lawrence Berkeley National Laboratory. There are two typical modes of operation of the ALS storage ring. In multibunch mode, the ring is filled to a current of 400 mA in 276 consecutive bunches with a single "camshaft" bunch located in the middle of
Research Interests:
Advanced Light Source (ALS) is one of the first 3rd-generation synchrotron light sources and it has been in operation at the Berkeley Lab since 1993. In the present ALS operation scenario, 1.5GeV electron beam is injected from the booster... more
Advanced Light Source (ALS) is one of the first 3rd-generation synchrotron light sources and it has been in operation at the Berkeley Lab since 1993. In the present ALS operation scenario, 1.5GeV electron beam is injected from the booster into the storage ring every 8 hours where it is accelerated to the final energy of 1.9GeV. The beam decays between