A5041140629- Photocathodes and Microchannel Plates
- Particle accelerators and beam dynamics
- Particle Accelerators and Free-Electron Lasers
- Diamond and Carbon-based Materials Research
- Electron and X-Ray Spectroscopy Techniques
- Quantum and electron transport phenomena
- Radiation Detection and Scintillator Technologies
- Topological Materials and Phenomena
- Semiconductor materials and devices
- Gyrotron and Vacuum Electronics Research
- X-ray Spectroscopy and Fluorescence Analysis
- Atomic and Subatomic Physics Research
- Superconducting Materials and Applications
- Advanced Surface Polishing Techniques
- Electronic and Structural Properties of Oxides
- Advanced Chemical Physics Studies
- Advanced X-ray Imaging Techniques
- Advanced Semiconductor Detectors and Materials
- High-pressure geophysics and materials
- Dark Matter and Cosmic Phenomena
- Semiconductor materials and interfaces
- Surface and Thin Film Phenomena
- Particle Detector Development and Performance
- Radiation Therapy and Dosimetry
- Advanced Electron Microscopy Techniques and Applications
Brookhaven National Laboratory
2015-2025
Los Alamos National Laboratory
2018
Max Planck Institute for Physics
2018
Argonne National Laboratory
2018
United States Naval Research Laboratory
2018
Naval Research Laboratory Materials Science and Technology Division
2018
Stony Brook University
2009-2014
IBM Research - Thomas J. Watson Research Center
2012
National Institute of Standards and Technology
2012
Abstract High brightness, high charge electron beams are critical for a number of advanced accelerator applications. The initial emittance the beam, which is determined by mean transverse energy (MTE) and laser spot size, one most important parameters determining beam quality. bialkali photocathodes illuminated visible have advantages quantum efficiency (QE) low MTE. Furthermore, Superconducting Radio Frequency (SRF) guns can operate in continuous wave (CW) mode at accelerating gradients,...
Alkali antimonides are well established as high efficiency, low intrinsic emittance photocathodes for accelerators and photon detectors. However, conventionally grown alkali antimonide films polycrystalline with surface disorder roughness that can limit achievable beam brightness. Ordering the crystalline structure of has potential to deliver higher brightness electron beams by reducing enabling engineering material properties at level atomic layers. In this report, we demonstrate growth...
The development of high-brightness electron sources is critical to state-of-the-art accelerator applications like X-ray free laser (XFEL) and ultra-fast microscopy. Cesium telluride chosen as the source material for multiple cutting-edge XFEL facilities worldwide. This manuscript presents first demonstration growth highly crystalized epitaxial cesium thin films on 4H-SiC graphene/4H-SiC substrates with ultrasmooth film surfaces. ordering was characterized by in situ reflection high energy...
Cooling of beams gold ions using electron bunches accelerated with radio-frequency systems was recently experimentally demonstrated in the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. Such an approach is new and opens possibility this technique higher energies than possible electrostatic acceleration beams. The challenges include generation suitable for cooling, delivery required quality to cooling sections without degradation beam angular divergence energy spread,...
GaAs photocathodes are the primary choice for generating spin-polarized electron beam with high brightness, polarization, and fast polarization reversal. However, it suffers from short lifetime due to highly reactive nature of emission surface, resulting in substantial operational difficulties. Activating a more robust material, such as Cs2Te, shows comparable that Cs–O activation increases robustness Cs2Te layer. previously reported based on Cs–Te suffer 10× lower quantum efficiency (QE)...
Ultra-flat, ultra-thin alkali antimonide photocathodes with high crystallinity can exhibit quantum efficiency and low mean transverse energy of outgoing electrons, which are essential requirements for a variety applications photocathode materials. Here, we investigate the growth Cs3Sb on graphene-coated 4H–SiC (Gr/4H–SiC), 3C–SiC, Si3N4 substrates. Sb is deposited using pulsed laser deposition, while Cs thermally simultaneously. We demonstrate, employing x-ray analysis measurements, that...
Hard x-ray photoelectron spectroscopy was applied to investigate the diamond-metal Schottky barrier heights for several metals and diamond surface terminations. The position of valence-band maximum determined by theoretically calculating density states applying cross section corrections. diamond-platinum height lowered 0.2 eV after thermal annealing, indicating annealing may increase carrier injection in devices leading photoconductive gain. platinum contacts on oxygen-terminated found...
K2CsSb is a promising photocathode candidate to serve as an electron source in next-generation light sources such Free Electron Lasers (FEL) and Energy Recovery Linacs (ERL). As the traditional recipe for creation of photocathodes typically results rough surface that deteriorates beam quality, significant effort has been made explore novel growth methods photocathodes. In this paper, method ternary co-evaporation K, Cs, Sb described. By using in-situ synchrotron X-ray techniques, quality...
K-Cs-Sb bialkali antimonide photocathodes grown by a triple-element codeposition method have been found to excellent quantum efficiency (QE) and outstanding near-atomic surface smoothness employed in the VHF gun Advanced Photoinjector Experiment (APEX), however, their robustness terms of lifetime at elevated photocathode temperature has not yet investigated. In this paper, relationship between The origin significant QE degradation temperatures over $70\text{...
Cesium telluride (CsTe) photocathodes have been the primary choice for electron sources by worldwide accelerators, due to their high quantum yield, stable performance in complex operation environments and long lifetime. In this paper we compared traditional sequential newly developed coevaporation growth of CsTe describing chemical structural evolution each method, using situ, real time x-ray characterization. From codeposition were able achieve ∼2 nm surface roughness, crystallinity a...
Bi-alkali antimonide photocathodes are one of the best known sources electrons for high current and/or bunch charge applications like Energy Recovery Linacs or Free Electron Lasers. Despite their quantum efficiency in visible light and low intrinsic emittance, surface roughness these prohibits use as emittance cathodes accelerating gradient superconducting normal conducting radio frequency photoguns limits minimum possible near threshold. Also, growth process materials is largely based on...
Two transmission-mode diamond X-ray beam position monitors installed at National Synchrotron Light Source (NSLS) beamline X25 are described. Each monitor is constructed around two horizontally tiled electronic-grade (p.p.b. nitrogen impurity) single-crystal (001) CVD synthetic diamonds. The position, angle and flux of the white can be monitored in real time with a resolution 500 nm horizontal direction 100 vertical for 3 mm × 1 beam. first has been operation more than one year without any...
Fabrication and testing of a prototype transmission-mode pixelated diamond X-ray detector (pitch size 60-100 µm), designed to simultaneously measure the flux, position morphology an beam in real time, are described. The pixel density is achieved by lithographically patterning vertical stripes on front horizontal back electronic-grade chemical vapor deposition single-crystal diamond. bias rotated through current read out at rate ∼ 1 kHz, which leads image sampling 30 Hz. This novel signal...
Advanced photoinjectors, which are critical to many next generation accelerators, open the door new ways of material probing, both as injectors for free electron lasers and ultra-fast diffraction. For these applications, nonuniformity electric field near cathode caused by surface roughness can be dominant source beam emittance. Therefore, improving photocathode while maintaining quantum efficiency is essential improvement brightness. In this paper, we report demonstration a bi-alkali...
Reduction of roughness to the nm level is critical achieving ultimate performance from photocathodes used in high gradient fields. The thrust this paper explore evolution during sequential growth, and show that deposition multilayer structures consisting very thin reacted layers results an smooth photocathode. Synchrotron x-ray methods were applied study multi-step growth process a efficiency K2CsSb A transition point Sb film grown on Si was observed at thickness ~40 Å with substrate...
Abstract This study reports successful deposition of high quantum efficiency (QE) bialkali antimonide K 2 CsSb photocathodes on graphene films. The results pave the way for an ultimate goal encapsulating technologically relevant accelerator technology with atomically thin protecting layer to enhance lifetime while minimizing QE losses. A 17% at ≈3.1 eV (405 nm) is highest value reported so far substrates and comparable that obtained stainless steel nickel reference substrates. spectral...
Alkali antimonide photocathodes have wide applications in free-electron lasers and electron cooling. The short lifetime of alkali necessitates frequent replacement the during a beam operation. Furthermore, exposure to mediocre vacuum causes loss photocathode quantum efficiency due chemical reaction with residual gas molecules. Theoretical analyses shown that covering an monolayer graphene or hexagonal boron nitride protects it coarse environment inhibition reactions require ultra-high...
The Low Energy RHIC electron Cooling (LEReC) project at Brookhaven National Laboratory recently demonstrated for the first time cooling of hadron bunches with radio-frequency (rf) accelerated bunches. LEReC uses a high-voltage photoemission gun stringent requirements beam current, quality, and stability. has photocathode high-power fiber laser, novel cathode production, transport, exchange system. It been that can continually produce high-current quality suitable cooling. We describe...
A high-current high-brightness electron accelerator for low-energy RHIC cooling (LEReC) was successfully commissioned at Brookhaven National Laboratory. The LEReC includes a dc photoemission gun, laser system, photocathode delivery magnets, beam diagnostics, superconducting rf booster cavity, and set of normal conducting cavities to provide enough flexibility tune the in longitudinal phase space. Cooling with nonmagnetized accelerated beams requires corrections obtain small momentum spread...
The lifetime of GaAs photocathodes in polarized electron guns is limited due to the delicate activation layer. An atomically clean and smooth surface needed deposit a robust layer, such as Cs2Te, with longer compared traditional (Cs,O) activation. A previous experiment Cs2Te on used heat cleaning temperatures around 400°C avoid an increase roughness [Bae et al., Appl. Phys. Lett. 112, 154101 (2018)]. High-temperature 580°C, which results relatively contamination-free surface, could be one...
Photocathodes based on bialkali antimonides have great potential in the field of high-brightness electron sources. In this paper, influence incident light absorption performance ${\mathrm{K}}_{2}\mathrm{CsSb}$ photocathodes was studied using Monte Carlo simulations. The surface plasmon polaritons (SPPs) were first introduced into employing a nanopattern structure to improve effective and adjust initial distribution photoelectrons. To evaluate effect SPPs photocathode performance,...
Diamond X-ray detectors with conducting nitrogen-incorporated ultra-nanocrystalline diamond (N-UNCD) films as electrodes were fabricated to measure beam flux and position. Structural characterization functionality tests performed for these devices. The N-UNCD grown on unseeded substrates compared a seeded silicon substrate. feasibility of the acting was confirmed by stable performance in monochromatic beam. fabrication process is able change surface status which may influence signal...
Quantum efficiency (QE) enhancement in accelerator technology relevant to antimonide photocathodes (K 2 CsSb) is achieved by interfacing them with atomically thin 2D crystal layers. The occurs a reflection mode, when placed between the and optically reflective substrates. Specifically, peak QE at 405 nm (3.1 eV) increases relative 10%, whereas long wavelength response 633 (2.0 36% on average up 80% localized “hot spot” regions are deposited onto graphene‐coated stainless steel. There similar...
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Erik M. Muller, Mengjia Gaowei, Ilan Ben-Zvi, Dimitre A. Dimitrov, John Smedley; Carbon edge response of diamond devices. Appl. Phys. Lett. 3 March 2014; 104 (9): 093515. https://doi.org/10.1063/1.4868135 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks...
Alkali antimonide photocathodes are a strong contender for the cathode of choice next-generation photon sources such as LCLS II or XFEL. These materials have already found extensive use in photodetectors and image intensifiers. However, only recently modern synchrotron techniques enabled systematic study formation chemistry these materials. Such analysis has led to understanding that inherently rough when grown through traditional sequential deposition; this roughness detrimental impact on...