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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Design and Implementation of an Acoustic X-ray Detector to Measure the LCLS Beam Energy

On April 11, 2009, first light was seen from LCLS. The present apparatus being used to measure the x-ray beam energy is the Total Energy Sensor which uses a suite of thermal sensors. Another device is needed to cross-check the energy measurements. This new diagnostic tool utilizes radiation acoustic phenomena to determine the x-ray beam energy. A target is hit by the x-rays from the beam, and a voltage is generated in two piezoelectric sensors attached to the target in response to the consequent deformation. Once the voltage is known, the power can be obtained. Thermal sensors will also be attached to the target for calibration purposes. Material selection and design were based on: durability, ultra-high vacuum compatibility, safety and thermal properties. The target material was also chosen for its acoustic properties which were determined from tests using a frequency generator and laser. Initial tests suggest the device will function as anticipated.

Loos, Jennifer L.↗
DOE OSTI2010

LCLS Undulator Fiducialization Plan

This note presents the LCLS undulator fiducialization plan. The undulators will be fiducialized in the Magnetic Measurement Facility at SLAC. The note begins by summarizing the requirements for the fiducialization. A brief discussion of the measurement equipment is presented, followed by the methods used to perform the fiducialization and check the results. This is followed by the detailed fiducialization plan in which each step is enumerated. Finally, the measurement results and data storage format are presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

The Turn-on of LCLS: the X-Ray Free Electron Laser at SLAC ( Keynote - 2011 JGI User Meeting)

The U.S. Department of Energy Joint Genome Institute (JGI) invited scientists interested in the application of genomics to bioenergy and environmental issues, as well as all current and prospective users and collaborators, to attend the annual DOE JGI Genomics of Energy & Environment Meeting held March 22-24, 2011 in Walnut Creek, Calif. The emphasis of this meeting was on the genomics of renewable energy strategies, carbon cycling, environmental gene discovery, and engineering of fuel-producing organisms. The meeting features presentations by leading scientists advancing these topics. SLAC National Laboratory Director Persis Drell gives a keynote talk on "The Turn-on of LCLS: the X-Ray Free-Electron Laser at SLAC" at the 6th Genomics of Energy & Environment Meeting on March 22, 2011

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

LCLS RF Station Phase Anomaly Candidate Dataset

A public anomaly detection dataset constructed from RF station faults for phase at SLAC's LCLS (Linac Coherent Light Source). We have compiled a dataset of the RF station diagnostic phase data and the beam-position monitor (BPM) signals, alongside the hand labels, for a labeled study period. The dataset consists of two HDF5 files (one for train and one for test) containing the raw data, two CSV files containing information about the candidates. The CSV file for the test dataset also contains the label.

Liang, Jia [Stanford Univ., CA (United States). In↗
DOE OSTI2011

Shielding Calculations for the Hard X-Rays Generated by LCLS Mec Laser System

Linac Coherent Light Source (LCLS) Matter in Extreme Conditions (MEC) Instrument is an X-ray instrument that will be able to create and diagnose High Energy Density (HED) matter. The MEC laser system can generate hard X-ray due to the interaction of the laser and the plasma. This paper summarizes results of the shielding calculations performed to evaluate the radiation hazards induced by this hard X-ray source with Monte Carlo code FLUKA. The dose rates and photon spectra due to this X-ray source are calculated at different locations with different shielding. The influence of the electron temperature on the source terms and the shielding effectiveness was also investigated.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

Time-resolved pump-probe experiments at the LCLS

The first time-resolved x-ray/optical pump-probe experiments at the SLAC Linac Coherent Light Source (LCLS) used a combination of feedback methods and post-analysis binning techniques to synchronize an ultrafast optical laser to the linac-based x-ray laser. Transient molecular nitrogen alignment revival features were resolved in time-dependent x-ray-induced fragmentation spectra. These alignment features were used to find the temporal overlap of the pump and probe pulses. The strong-field dissociation of x-ray generated quasi-bound molecular dications was used to establish the residual timing jitter. This analysis shows that the relative arrival time of the Ti:Sapphire laser and the x-ray pulses had a distribution with a standard deviation of approximately 120 fs. The largest contribution to the jitter noise spectrum was the locking of the laser oscillator to the reference RF of the accelerator, which suggests that simple technical improvements could reduce the jitter to better than 50 fs.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Identifying Longitudinal Jitter Sources in the LCLS Linac

The Linac Coherent Light Source (LCLS) at SLAC is an x-ray Free Electron Laser (FEL) with wavelengths of 0.15 nm to 1.5 nm. The electron beam stability is important for good lasing. While the transverse jitter of the beam is about 10-20% of the rms beam sizes, the jitter in the longitudinal phase space is a multiple of the energy spread and bunch length. At the lower energy of 4.3 GeV (corresponding to the longest wavelength of 1.5 nm) the relative energy jitter can be 0.125%, while the rms energy spread is with 0.025% five times smaller. An even bigger ratio exists for the arrival time jitter of 50 fs and the bunch duration of about 5 fs (rms) in the low charge (20 pC) operating mode. Although the impact to the experiments is reduced by providing pulse-by-pulse data of the measured energy and arrival time, it would be nice to understand and mitigate the root causes of this jitter. The thyratron of the high power supply of the RF klystrons is one of the main contributors. Another suspect is the multi-pacting in the RF loads. Phase measurements down to 0.01 degree (equals 10 fs) along the RF pulse were achieved, giving hints to the impact of the different sources.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Linac Energy Management for LCLS

Linac Energy Management (LEM) is a control system program that scales magnet field set-point settings following a change in beam energy. LEM is necessary because changes in the number, phase, and amplitude of the active klystrons change the beam's rigidity, and therefore, to maintain constant optics, one has to change focusing gradients and bend fields accordingly. This paper describes the basic process, the control system application programs we developed for LEM, and some of the implementation lessons learned at the Linac Coherent Light Source (LCLS).

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Microbunching phenomena in LCLS-II

The microbunching instability has long been recognized as a potential limiting factor to the performance of X-ray FELs. It is of particular relevance in LCLS-II due, in part, to a layout that includes a long bypass beamline between the Linac and the undulators. Here we focus on two aspects of the instability that highlight the importance of 3D effects.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Quench Studies of Six High Temperature Nitrogen Doped 9 Cell Cavities for Use in the LCLS-II Baseline Prototype Cryomodule at Jefferson Laboratory

Jefferson Lab (JLab) processed six nine-cell cavities as part of a small-scale production for LCLS-II cavity processing development utilizing the promising nitrogen-doping process. Various nitrogen-doping recipes have been scrutinized to optimize process parameters with the aim to guarantee an unloaded quality factor (Q_0) of 2.7∙10 10 at an accelerating field (Eacc) of 16 MV/m at 2.0 K in the cryomodule. During the R&D phase the characteristic Q0 vs. Eacc performance curve of the cavities has been measured in JLab’s vertical test area at 2 K. The findings showed the characteristic rise of the Q0 with Eacc as expected from nitrogen-doping. Initially, five cavities achieved an average Q0 of 3.3·10 10 at the limiting Eacc averaging to 16.8 MV/m, while one cavity experienced an early quench accompanied by an unusual Q_0 vs. Eacc curve. The project accounts for a cavity performance loss from the vertical dewar test (with or without the helium vessel) to the horizontal performance in a cryomodule, such that these results leave no save margin to the cryomodule specification. Consequently, a refinement of the nitrogen-doping has been initiated to guarantee an average quench field above 20 MV/m without impeding the Q_0. This paper covers the refinement work performed for each cavity, which depends on the initial results, as well as a quench analysis carried out before and after the rework during the vertical RF tests as far as applicable.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

The LCLS-II LLRF System

The SLAC National Accelerator Laboratory is planning an upgrade (LCLS-II) to the Linear Coherent Light Source with a 4 GeV CW superconducting (SCRF) linac. 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 Q L of ~ 4x10 7 . The RF system will have 3.8 kW solid state amplifiers driving single cavities. 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 RF stations (Forward, Reflected and Drive signals). 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) is being modeled and cavity microphonic testing has started. This paper describes the LLRF system under consideration, including recent modeling and cavity tests.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Status of LCLS - II QA Systems Collaboration for Cyromodule Construction at TJNAF and FNAL

At the Thomas Jefferson National Accelerator Facility (Jefferson Lab), we are supporting the LCLS-II Project at SLAC. The plan is to build thirty-five 1.3 GHz continuous wave cryomodules, production to be split between JLab and FNAL (Fermilab). This has required a close collaboration between the partner labs, including enhancing our existing quality systems to include this collaboration. This overview describes the current status of the Quality System development as of August 2015, when the partner labs start the assembly of the prototype cryomodules.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Transport of LCLS-II 1.3 Ghz cryomodule to SLAC

In a partnership with SLAC National Accelerator Laboratory (SLAC) and Jefferson Lab, Fermilab will assemble and test 17 of the 35 total 1.3 GHz cryomodules for the Linac Coherent Light Source II (LCLS-II) Project. These include a prototype built and delivered by each Lab. Another two 3.9 GHz cryomodules will be built, tested and transported by Fermilab to SLAC. Each assembly will be transported over-the-road from Fermilab or Jefferson Lab using specific routes to SLAC. The transport system consists of a base frame, isolation fixture and upper protective truss. The strongback cryomodule lifting fixture is described along with other supporting equipment used for both over-the-road transport and local (on-site) transport at Fermilab. Initially, analysis of fragile components and stability studies will be performed in order to assess the risk associated with over-the-road transport of a fully assembled cryomodule.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Fresh Slice Self-Seeding and Fresh Slice Harmonic Lasing at LCLS

We present results from the successful demonstration of fresh slice self-seeding at the Linac Coherent Light Source (LCLS).* The performance is compared with SASE and regular self-seeding at photon energy of 5.5 keV, resulting in a relative average brightness increase of a factor of 12 and a factor of 2 respectively. Following this proof-of-principle we discuss the forthcoming plans to use the same technique** for fresh slice harmonic lasing in an upcoming experiment. The demonstration of fresh slice harmonic lasing provides an attractive solution for future XFELs aiming to achieve high efficiency, high brightness X-ray pulses at high photon energies (>12 keV).***

Amann, J.W.↗
DOE OSTI2018

Superconducting Magnet Performance in LCLS-II Cryomodules

New LCLS-II Linear Superconducting Accelerator Cry-omodules are under construction at Fermilab. Installed in-side each SCRF Cryomodule is a superconducting magnet package to focus and steer an electron beam. The magnet package is an iron dominated configuration with conduc-tively cooled racetrack-type quadrupole and dipole coils. For easier installation the magnet can be split in the vertical plane. Initially the magnet was tested in a liquid helium bath, and high precision magnetic field measurements were performed. The first (prototype) Cryomodule with the magnet inside was built and successfully tested at Fermilab test facility. In this paper the magnet package is discussed, the Cryomodule magnet test results and current leads con-duction cooling performance are presented. So far magnets in nine Cryomodules were successfully tested at Fermilab.

Kashikhin, V.↗
DOE OSTI2019

Optimization of Clean Room Infrastructure and Procedure During LCLS-II Cryomodule Production at Fermilab

Optimization of Fermilab string assembly procedure and infrastructure has yielded a significant improvement of cryomodule particulate counts. Late production of LCLSII cryomodules were tested at CMTF at Fermilab and showed little to no x-ray up to administrative limit. The paper describes the field emission measurement instrumentation, field emission results of Fermilab’s LCLS-II cryomodules, clean room infrastructure upgrade and procedure optimization.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Magnetic Field Induced by Thermo Electric Current in LCLS-II Cryomodules

The Seebeck effect in metals plays an important role in cryomodule design and performance. As the cryomodule is cooled from room temperature to nominal cavity operating temperature of 2 K, components in the cryomodule experience varying temperatures. Some components such as power couplers have gradients from 300 K to 2 K. Such gradients and metallic paths form thermo-electric current loops that circulate through and around the niobium cavities. These currents will generate an additional magnetic field that could be trapped in the cavity wall during superconducting transition, as well as during cavity quench. This trapped field can degrade the cavity’s quality factor and increase heat load. A simple circuit model is proposed and compared to a calculated trapped field during LCLS-II cryomodule tests.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Fermilab ships first LCLS-II cryomodule to SLAC

The Linac Coherent Light Source at the Department of Energy's SLAC National Laboratory is an X-ray laser that allows scientists to take snapshots of atoms and molecules in motion, revealing fundamental processes in materials, technology and living things. Its strobe-like pulses are just a few millionths of a second long, and a billion times brighter than previous X-ray sources. Fermilab is providing SLAC with 22 cryomodules for the LCLS-II upgrade, which will take X-ray science to the next level, opening the door to a whole new range of studies of the ultrafast and ultrasmall. Learn more at: http://news.fnal.gov/2018/01/fermilab... http://lcls-ii.fnal.gov/ https://lcls.slac.stanford.edu/lcls-ii

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗