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Chase, Brian

Publications and source records attributed to Chase, Brian.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Passive Microphonics Mitigation during LCLS-II Cryomodule Testing at Fermilab

The LCLS-II project calls for cryomodule production and testing at both Fermilab and JLab. Due to low beam loading and high cavity quality factor, the designed peak detuning specification is 10 Hz. Initial testing showed peak detuning up to 150 Hz with a complex and varying time-structure, showing both fast (1-2 second) and slow (1-2 hour) drifts in amplitude and spectrum. Extensive warm and cold testing showed Thermoacoustic Oscillations in the cryogenic valves were the primary source of the microphonics. This was mitigated by valve wipers and valve re-plumbing, resulting in a greatly improved cavity detuning environment. Additional modifications were made to the cavity mechanical supports and Fermilab test stand to improve detuning performance. These modifications and testing results will be presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Active Microphonics Compensation for LCLS-II

Testing of early LCLS-II cryomodules showed microphonics-induced detuning levels well above specification. As part of a risk-mitigation effort, a collaboration was formed between SLAC, LBNL, and Fermilab to develop and implement active microphonics compensation into the LCLS-II LLRF system. Compensation was first demonstrated using a Fermilab FPGA-based development system compensating on single cavities, then with the LCLS-II LLRF system on single and multiple cavities simultaneously. The primary technique used for this effort is a bank of narrowband filter set using the piezo-to-detuning transfer function. Compensation automation, optimization, and stability studies were done. Details of the techniques used, firmware/software implementation, and results of these studies will be presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Design and Implementation of the LLRF System for LCLS-II

The SLAC National Accelerator Laboratory is building LCLS-II, a new 4 GeV CW superconducting (SCRF) linac as a major upgrade of the existing LCLS. The SCRF linac consists of 35 ILC style cryomodules (eight cavities each) for a total of 280 cavities. Expected cavity gradients are 16 MV/m with a loaded QL of ~ 4 x 10⁷. Each individual RF cavity will be powered by one 3.8 kW solid state amplifier. To ensure optimum field stability a single source single cavity control system has been chosen. It consists of a precision four channel cavity receiver and two RF stations (Forward, Reflected and Drive signals) each controlling two cavities. In order to regulate the resonant frequency variations of the cavities due to He pressure, the tuning of each cavity is controlled by a Piezo actuator and a slow stepper motor. In addition the system (LLRF-amplifier-cavity) was modeled and cavity microphonic testing has started. This paper will describe the main system elements as well as test results on LCLS-II cryomodules.

Serrano, Carlos↗
DOE OSTI2017

Commissioning And First Results From The Fermilab Cryomodule Test Stand

A new test stand dedicated to Superconducting Radiofrequency (SRF) cryomodule testing, CMTS1, has been commissioned and is now in operation at Fermilab. The first device to be cooled down and powered in this facility is the prototype 1.3 GHz cryomodule assembled at Fermilab for LCLS-II. We describe the demonstrated capabilities of CMTS1, report on steps taken during commissioning, provide an overview of first test results, and survey future plans.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Advanced, phase-locked, 100 kW, 1.3 GHz magnetron

Calabazas Creek Research, Inc., in collaboration with Fermilab and Communications & Power Industries, LLC, is developing a phase-locked, 100 kW peak, 10 kW average power magnetron-based RF system for driving accelerators. Here, phase locking will be achieved using an approach originating at Fermilab that includes control of both amplitude and phase on a fast time scale.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Modular Low-Noise Piezoamplifier Driver for SRF Applications

Controlling the resonant frequency of superconducting cavities can be difficult due to their high sensitvity to mechanical and pressure variations. In addition, the cooling process itself as well as RF heating and deformation leads to resonant frequency shifts that need to be mechanicalyl compensated for. Stepper motors are often used for gross adjustment, but they also introduce significant noise in to the cavity system. Piezo transducers provide a way to perturb the cavity with minimal disruption. For the LCLS-II project, a modular piezoamplifier driver was developed using off-the-shelf components in conjunction with a custom carrier board. This allows for a low-noise system that provides real-time monitoring of piezotransducer health. The modules are designed to be easily serviceable and use audio-style connectors for monitor and drive ports on the chassis.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

SoC Architectures in LLRF at Fermilab

System-On-Chip (SoC) designs refers to devices where a front-end processing system is in the same package as peripherals, in particular an FPGA fabric. The tightly-coupled design allows for very high data rates, easily reaching several Gbps from an FPGA RF signal chain to front-end processing.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Resonant Control for Fermilab's PXIE RFQ

The RFQ for Fermilab's PXIE test program is designed to accelerate a < 10 mA H⁻ CW beam to 2.1 MeV. The RFQ has a four-vane design, with four modules brazed together for a total of 4.45 m in length. The RF power required is < 130 kW at 162.5 MHz. A 3 kHz limit on the maximum allowable frequency error is imposed by the RF amplifiers. This frequency constraint must be managed entirely through differential cooling of the RFQ's vanes and outer body and associated material expansion. Simulations indicate that the body and vane coolant temperature should be controlled to within 0.1 degrees C. We present the design of the cooling network and the resonant control algorithm for this structure, as well as results from initial operation.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Neural Network Model Of The PXIE RFQ Cooling System and Resonant Frequency Response

As part of the PIP-II Injector Experiment (PXIE) accel-erator, a four-vane radio frequency quadrupole (RFQ) accelerates a 30-keV, 1-mA to 10-mA H' ion beam to 2.1 MeV. It is designed to operate at a frequency of 162.5 MHz with arbitrary duty factor, including continuous wave (CW) mode. The resonant frequency is controlled solely by a water-cooling system. We present an initial neural network model of the RFQ frequency response to changes in the cooling system and RF power conditions during pulsed operation. A neural network model will be used in a model predictive control scheme to regulate the resonant frequency of the RFQ.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

LLRF Control of High Loaded-Q Cavities for the LCLS-II

The SLAC National Accelerator Laboratory is planning an upgrade (LCLS-II) to the Linear Coherent Light Source with a 4 GeV CW Superconducting Radio Frequency (SCRF) linac. The nature of the machine places stringent requirements in the Low-Level RF (LLRF) system, expected to control the cavity fields within 0.01 degrees in phase and 0.01% in amplitude, which is equivalent to a longitudinal motion of the cavity structure in the nanometer range. This stability has been achieved in the past but never for hundreds of superconducting cavities in Continuous-Wave (CW) operation. The difficulty resides in providing the ability to reject disturbances from the cryomodule, which is incompletely known as it depends on the cryomodule structure itself (currently under development at JLab and Fermilab) and the harsh accelerator environment. Previous experience in the field and an extrapolation to the cavity design parameters (relatively high Q_{L}c≈ 4×10⁷ , implying a half-bandwidth of around 16 Hz) suggest the use of strong RF feedback to reject the projected noise disturbances, which in turn demands careful engineering of the entire system.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

First Beam and High-Gradient Cryomodule Commissioning Results of the Advanced Superconducting Test Accelerator at Fermilab

The advanced superconducting test accelerator at Fermilab has accelerated electrons to 20 MeV and, separately, the International Linear Collider (ILC) style 8-cavity cryomodule has achieved the ILC performance milestone of 31.5 MV/m per cavity. When fully completed, the accelerator will consist of a photoinjector, one ILC-type cryomodule, multiple accelerator R&D beamlines, and a downstream beamline to inject 300 MeV electrons into the Integrable Optics Test Accelerator (IOTA). We report on the results of first beam, the achievement of our cryomodule to ILC gradient specifications, and near-term future plans for the facility.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

High-Power Magnetron Transmitter for the Electron Collider Ring of the MEIC Facility

Operation of the 3-12 GeV electron collider 8-shape ring of the MEIC facility causes a Synchrotron Radiation (SR) of electrons in arcs with energy loss of ~20 kW/m at beam current of ~3 A. The total SR loss up to 2 MW per a revolution is presumed to compensate by Superconducting RF (SRF) accelerating cavities. To minimize the beam emittance, each individual SRF cavity is proposed to feed by an individual and independent RF source allowing a wide-band control in phase and power. Most efficient and less expensive in capital and maintenance costs the high-power transmitters based on magnetrons, injection-locked by phase-modulated signals, controlled in wide-band are proposed as the RF sources. The magnetron RF sources utilizing 2-cascade magnetrons allowing a wide-band phase and power control by the injection-locking phase-modulated signals were experimentally modelled by 2.45 GHz, CW, 1 kW magnetrons. Results of the modelling and adequacy of the transmitters for the SRF cavities are discussed in the presented article.

Kazakevich, Grigory↗
DOE OSTI2015

Precision vector control of a superconducting RF cavity driven by an injection locked magnetron

The technique presented in this paper enables the regulation of both radio frequency amplitude and phase in narrow band devices such as a Superconducting RF (SRF) cavity driven by constant power output devices i.e. magnetrons [1]. The ability to use low cost high efficiency magnetrons for accelerator RF power systems, with tight vector regulation, presents a substantial cost savings in both construction and operating costs - compared to current RF power system technology. An operating CW system at 2.45 GHz has been experimentally developed. Vector control of an injection locked magnetron has been extensively tested and characterized with a SRF cavity as the load. Amplitude dynamic range of 30 dB, amplitude stability of 0.3% r.m.s, and phase stability of 0.26 degrees r.m.s. has been demonstrated.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

SRF Systems for ASTA at Fermilab

The Advanced Superconducting Test Accelerator (ASTA) at Fermilab now being commissioned is comprised of a number of superconducting RF systems including single-cavity cryomodules and a TESLA/ILC style 8-cavity cryomodule. Two of them, 'Capture Cavity 2' and 'Cryomodule 2', have been cooled to 2 Kelvin and brought into operation. We provide an overview of the unique characteristics of each of the systems, commissioning experience, and latest results including their respective operating characteristics.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

Performance of Ferrite Vector Modulators in the LLRF System of the Fermilab HINS 6-Cavity Test

The High Intensity Neutrino Source (HINS) 6-cavity test is a part of the Fermilab HINS Linac R&D program for a low energy, high intensity proton Hsup>- linear accelerator. One of the objectives of the 6-cavity test is to demonstrate the use of high power RF Ferrite Vector Modulators(FVM) for independent control of multiple cavities driven by a single klystron. The beamline includes an RFQ and six cavities. The LLRF system provides a primary feedback loop around the RFQ and the distribution of the regulated klystron output is controlled by secondary learning feed-forward loops on the FVMs for each of the six cavities. The feed-forward loops provide pulse to pulse correction to the current waveform profiles of the FVM power supplies to compensate for beam-loading and other disturbances. The learning feed-forward loops are shown to successfully control the amplitude and phase settings for the cavities well within the 1 % and 1 degree requirements specified for the system.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

A Two-stage Injection-locked Magnetron for Accelerators with Superconducting Cavities

A concept for a two-stage injection-locked CW magnetron intended to drive Superconducting Cavities (SC) for intensity-frontier accelerators has been proposed. The concept considers two magnetrons in which the output power differs by 15-20 dB and the lower power magnetron being frequency-locked from an external source locks the higher power magnetron. The injection-locked two-stage CW magnetron can be used as an RF power source for Fermilab's Project-X to feed separately each of the 1.3 GHz SC of the 8 GeV pulsed linac. We expect output/locking power ratio of about 30-40 dB assuming operation in a pulsed mode with pulse duration of ~ 8 ms and repetition rate of 10 Hz. The experimental setup of a two-stage magnetron utilising CW, S-band, 1 kW tubes operating at pulse duration of 1-10 ms, and the obtained results are presented and discussed in this paper.

43 PARTICLE ACCELERATORS↗