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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

The dynamic synthesis time-lag control for the 1.3 GHz LCLS-II Cryomodule test at Fermilab

The 1.3GHz LCLS-II Cryomodule (CM) has 8 cavities and each cavity has 9 RF cells and 80W heater. The 1.3GHz LCLS-II CM is 12.2-meter-long and contains a total 241.3 liters (equivalent liquid) of liquid helium, which is filling up by the 4KW@2.0K cryogenic plant at the Fermilab Cryomodule Test Facility (CMTF). The dynamic synthesis 2K cryogenic control system is built to control the long time-lag, unstable CM cryogenic system, under different modes operations. A report on the results obtained from the dynamic synthesis long time-lag control in the CMTF 1.3GHz CM test will be presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Commissioning plan for LCLS II 2 K cold box

Commissioning of the LCLS II cryogenic plant has been planned with respect to electrical and mechanical systems checkout, equipment cleanup, cool-down, and individual performance evaluation. This plant consists of warm and cold storage, helium compressors, 4.5 K and 2 K cold boxes, and all auxiliaries typical for helium refrigeration processes. The 2 K cold box, consisting of five cold compressors in series to produce the flow and pressures necessary for 2K operation, will be the last equipment installed and, along with an additional 10,000 L helium dewar, will allow the entire plant to be commissioned as a single entity. The pre-commissioning stages, commissioning plan for 2 K cold box without connecting to the LCLS II LINAC, additional test equipment needed to simulate the loads, all process studies and associated results are described herein.

36 MATERIALS SCIENCE↗
DOE OSTI2020

The ePix10k 2-megapixel hard X-ray detector at LCLS

The ePix10ka2M (ePix10k) is a new large area detector specifically developed for X-ray free-electron laser (XFEL) applications. The hybrid pixel detector was developed at SLAC to provide a hard X-ray area detector with a high dynamic range, running at the 120 Hz repetition rate of the Linac Coherent Light Source (LCLS). The ePix10k consists of 16 modules, each with 352 × 384 pixels of 100 µm × 100 µm distributed on four ASICs, resulting in a 2.16 megapixel detector, with a 16.5 cm × 16.5 cm active area and ∼80% coverage. The high dynamic range is achieved with three distinct gain settings (low, medium, high) as well as two auto-ranging modes (high-to-low and medium-to-low). Here the three fixed gain modes are evaluated. The resulting dynamic range (from single photon counting to 10000 photons pixel −1 pulse −1 at 8 keV) makes it suitable for a large number of different XFEL experiments. The ePix10k replaces the large CSPAD in operation since 2011. The dimensions of the two detectors are similar, making the upgrade from CSPAD to ePix10k straightforward for most setups, with the ePix10k improving on experimental performance. The SLAC-developed ePix cameras all utilize a similar platform, are tailored to target different experimental conditions and are designed to provide an upgrade path for future high-repetition-rate XFELs. Here the first measurements on this new ePix10k detector are presented and the performance under typical XFEL conditions evaluated during an LCLS X-ray diffuse scattering experiment measuring the 9.5 keV X-ray photons scattered from a thin liquid jet.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Thermodynamic Analyses of the LCLS-II Cryogenic Distribution System

The Linac Coherent Light Source (LCLS) at Stanford Linear Accelerator Center (SLAC) is in the process of being upgraded to a superconducting radio frequency (SRF) accelerator and renamed LCLS-II. This upgrade requires thirty-five 1.3 GHz SRF cryomodules (CM) and two 3.9 GHz CM. A cryogenic distribution system (CDS) is in development by Fermi National Accelerator Laboratory to interconnect the CM Linac with the cryogenic plant (CP). The CDS design utilizes cryogenic helium to support the CM operations with a high temperature thermal shield around 55 K, a low temperature thermal intercepts around 5 K, and a SRF cavity liquid helium supply and sub-atmospheric vapor return both around 2 K. Additionally the design must accommodate a Linac consisting of two parallel cryogenic strings, supported by two independent CP utilizing CDS components such as distribution boxes, transfer lines, feed caps and endcaps. In this paper, we describe the overall layout of the cryogenic distribution system and the major thermodynamic factors which influence the CDS design including heat loads, pressure drops, temperature profiles, and pressure relieving requirements. In addition the paper describes how the models are created to perform the analyses.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

A COMPACT BEAM SPREADER USING RF DEFLECTING CAVITIES FOR THE LCLS-II

The LCLS-II project currently under development is designed to accelerate electron bunches up to 4 GeV and transport them to one of two FEL undulators located more than 2 km downstream of the end of the LCLS-II linac. The upgrade requires a spreader system to separate the baseline electron bunches and transport them to two undulator lines or a local dump. Fast bipolar kickers (FK) or transverse electric rf deflectors (RFD) are considered as fast-switching devices (FSD). In the RFD approach described here three design options operating at 325 MHz are studied including a superconducting rf-dipole cavity, a normal conducting rf-dipole cavity, and a normal conducting 4-rod cavity. Optional compact splitting schemes involving a combination of vertical and horizontal initial deflections are addressed.

De Silva, S. U.↗
DOE OSTI2017

Status of the LCLS-II Accelerating Cavity Production

Cavity serial production for the LCLS-II 4 GeV CM SRF linac has started. A quantity of 266 accelerating cavities has been ordered from two industrial vendors. Jefferson Laboratory leads the cavity procurement activities for the project and has successfully transferred the Nitrogen-Doping process to the industrial partners in the initial phase, which is now being applied for the production cavities. We report on the results from vendor qualification and the status of the cavity production for LCLS-II.

Daly, Ed↗
DOE OSTI2018

LCLS-II Gun/Buncher LLRF System Design

For a free electron laser, the stability of injector is critical to the final electron beam parameters, e.g., beam energy, beam arrival time, and eventually it determines the photon quality. The LCLS-II project's injector contains a VHF copper cavity as the gun and a two-cell L-band copper cavity as its buncher. The cavity designs are inherited from the APEX design, but requires more field stability than demonstrated in APEX operation. The gun LLRF system design uses a connectorized RF front end and low noise digitizer, together with the same general purpose FPGA carrier board used in the LCLS-II SRF LLRF system. The buncher LLRF system directly adopts the SRF LLRF chassis design, but programs the controller to run the normal conducting cavities. In this paper, we describe the gun/buncher LLRF system design, including the hardware design, the firmware design and bench test.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Update on Plasma Processing R&D for LCLS-II

SRF cavities performance preservation is crucial, from vertical test to accelerator operation. Field emission is still one of the main problems to overcome and plasma cleaning has been proven successful by SNS, in cleaning field emitters and increasing the work function of Nb. A collaboration has been established between FNAL, SLAC and ORNL with the purpose of applying plasma processing to LCLS-II cavities, in order to minimize and overcome field emission without affecting the high Q of N-doped cavities. The recipe will follow the neon-oxygen active plasma adopted at SNS, allowing in-situ processing of cavities and cryomodules from hydrocarbon contaminants. A novel method for plasma ignition has been developed at FNAL: a plasma glow discharge is ignited using high order modes to overcome limitations imposed by the fundamental power coupler. The results of experiments on 9-cell LCLS-II cavity are presented, along with plasma ignition studies. In addition the RF system is shown and N-doped Nb samples studies are discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Tuner Testing of a Dressed 3.9 GHz Cavity for LCLS-II at Fermilab

Fermilab is responsible for the design of the 3.9 GHz cryomodule for LCLS-II. Integrated acceptance testing of a dressed 3.9 GHz cavity for the LCLS-II project has been done at the Fermilab Horizontal Test Stand. This test included a slim blade tuner (based on INFN & XFEL designs) with integrated piezoelectric fast/fine tuner. This paper will present results of the mechanical setup, cold testing, and cold function of this tuner including fast and slow tuner range, sensitivity, and hysteresis.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Design and Test Results of the 3.9 GHz Cavity for LCLS-II

The LCLS-II project uses sixteen 3.9 GHz superconduct-ing cavities to linearize energy distribution before the bunch compressor. To meet LCLS-II requirements origi-nal FNAL design used in FLASH and XFEL was signifi-cantly modified to improve performance and provide reliable operation up to 16 MV/m in cw regime [1-3]. Four prototype cavities were built and tested at vertical cryo-stat. After dressing, one cavity was assembled and tested at horizontal cryostat as part of design verification pro-gram. All auxiliaries (magnetic shielding, power and HOM couplers, tuner) were also re-designed and tested with this cavity. In this paper we will discuss cavity and coupler design and test results.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Commissioning of the LCLS-II Prototype HOM Detectors with Tesla-Type Cavities at Fast

Experiments at the Fermilab Accelerator Science and Technology* (FAST) facility detected electron beam-induced high order mode (HOM) signals from Tesla superconducting cavities. This paper describes some of the signal detection hardware used in this experiment, as well as measurements of the HOM signal magnitude versus beam trajectory. These measurements were made both with a single bunch and with a train of 50 bunches at bunch charges from 400 pC/b down to 10 pC/b. The detection hardware is designed for use with the Tesla superconducting cavities of LCLS-II at SLAC** and is based on a prototype already in use at Fermilab. The HOM signal passes through a bandpass filter that is centered on several cavity dipole modes and a zero bias Schottky diode detects its magnitude. Direct comparisons were made between the FNAL chassis and the SLAC prototype for identical beam steering conditions. To support measurements with bunch charges as low as 10 pC, the SLAC detector has RF amplification between the bandpass filter and the diode detector. With this hardware, usable HOM signal measurements are obtained with a single bunch of 10 pC in cryomodule cavities as will be needed for LCLS-II.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Monopole HOMs Dumping in the LCLS-II 1.3 GHz Structure

Developing an upgrade of Linac Coherent Light Source (LCLS-II) is currently underway. The central part of LCLS-II is a continuous wave superconducting RF (CW SRF) electron linac. High order modes (HOMs) excited in SRF structures by passing beam may deteriorate beam quality and affect beam stability. In this paper we report the simulation results of monopole High Order Modes (HOM) spectrum in the 1.3 GHz accelerating structure. Optimum parameters of the HOM feedthrough are suggested for minimizing RF losses on the HOM antenna tip and for preserving an efficiency of monopole HOMs damping simultaneously.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Thermal-Mechanical Study of 3.9 GHz CW Coupler and Cavity for LCLS-II Project

Third harmonic system was originally developed by Fermilab for FLASH facility at DESY and then was adopted and modified by INFN for the XFEL project [1-3]. In contrast to XFEL project, all cryomodules in LCLS-II project will operate in CW regime with higher RF average power for 1.3 GHz and 3.9 GHz cavities and couplers. Design of the cavity and fundamental power coupler has been modified to satisfy LCLS-II requirements. In this paper we discuss the results of COMSOL thermal and mechanical analysis of the 3.9 GHz coupler and cavity to verify proposed modifica-tion of the design. For the dressed cavity we present simulations of Lorentz force detuning, helium pressure sensitivity df/dP and major mechanical resonances.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

LCLS-II and HE Cryomodule Microphonics at CMTF at Fermilab

Microphonics causes the cavity to detune. This study discusses the microphonics of 16 cryomodules, 14 for LCLS-II and 2 for LCLS-II HE tested at CMTF. The peak detuning, as well as the RMS detuning for each cryomodule, will be discussed. For each cryomodule, the data was taken with enough soaking time to prevent any thermalization effects which can show up in the detuning. Each data capture taken was 30 minutes or longer and sampled at 1 kHz.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

High Precision RF Control for SRF Cavities in LCLS-II

The unique properties of SRF cavities enable a new generation of X-ray light sources in XFEL and LCLS-II. The LCLS-II design calls for 280 L-band cavities to be operated in CW mode with a Q_{L} of 4x10⁷, using Single-Source Single-Cavity control. The target RF field stability is 0.01% and 0.01 degree for the band above 1 Hz. Hardware and software implementing a digital LLRF system has been constructed by a four-lab collaboration to minimize known contributors to cavity RF field fluctuation. Efforts include careful attachment to the phase reference line, and minimizing the effects of RF crosstalk by placing forward and reverse signals in chassis separate from the cavity measurement. A low-noise receiver/digitizer section will allow feedback to operate with high proportional gain without excessive noise being sent to the drive amplifier. Test results will show behavior on prototype cryomodules at FNAL and JLab, ahead of the 2018 final accelerator installation.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

LCLS-II CRYOMODULE TRANSPORT SYSTEM TESTING

The Cryomodules (CM) for the Linear Coherent Light Source II (LCLS-II) will be shipped to SLAC (Menlo Park, California) from JLab (Newport News, Virginia) and FNAL (Batavia, Illinois). A transportation system has been designed and built to safely transport the CMs over the road. It uses an array of helical isolator springs to attenuate shocks on the CM to below 1.5g in all directions. The system rides on trailers equipped with Air-Ride suspension, which attenuates vibration loads. The prototype LCLS-II CM (pCM) was driven 750 miles to test the transport system; shock loggers recorded the shock attenuation on the pCM and vacuum gauges were used to detect any compromises in beamline vacuum. Alignment measurements were taken before and after the trip to check whether cavity positions had shifted beyond the ± 0.2mm spec. Passband frequencies and cavity gradients were measured at 2K at the Cryomodule Test Facility (CMTF) at JLab to identify any degradation of CM performance after transportation. The transport system was found to have safely carried the CM and is cleared to begin shipments from JLab and FNAL to SLAC.

Huque, Naeem↗
DOE OSTI2019

3.9 GHz SRF Production Cavities for LCLS-II

The main part of the SRF linac for the Linac Coherent Light Source II (LCLS-II) at SLAC will consist of 35 cryomodules with superconducting RF cavities operating at 1.3 GHz. In addition, two cryomodules with 3.9 GHz cavities will be installed and help to linearize the longitudinal phase space of the beam. During the design verification phase, four prototype 9-cell 3.9 GHz cavities had been built by industry and then processed, including chemical surface removal and heat treatment, and tested at Fermi National Accelerator Laboratory. Based on the resulting cavity treatment recipe, 24 cavities (for two cryomodules to be installed in the linac and one spare cryomodule) have been built by industry and tested at Fermilab prior to cryomodule string assembly. We present an overview of the cavity production and the results of the vertical acceptance tests for the LCLS-II 3.9 GHz cavities.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Overview of LCLS-II Project Status at Fermilab

The superconducting RF Continuous-Wave (CW) Linac for the LCLS-II consists of thirty-five 1.3 GHz and two 3.9 GHz cryomodules that Fermilab and Jefferson Lab are jointly producing in collaboration with SLAC. Fermilab’s scope of work is to build, test, and deliver half the 1.3 GHz and all the 3.9 GHz cryomodules and to design and procure components for the cryogenic distribution system. Fermilab has primary responsibility for delivering a working design. The cryomodule design basis was the European XFEL but several elements evolved to meet CW operation requirements and specifics of the SLAC tunnel. There have been several challenges faced during the design, assembly, testing and transportation of the cryomodules which have required design updates. Success in overcoming these challenges is attributable to the strength of the LCLS-II SRF Collaboration (Fermilab, Jefferson Lab and SLAC with extensive help from DESY and CEA/Saclay). The cryogenic distribution system has progressed relatively well and there are valuable Lessons Learned. An overview of the status, accomplishments, problems encountered, solutions developed, and a summary of Lessons Learned will be presented.

43 PARTICLE ACCELERATORS↗