| Paper |
Title |
Page |
TUOBB4 |
Measurement of Ultrasmall Transverse Spot Size |
|
| |
- K.G. Roberts, R.K. Li, P. Musumeci
UCLA, Los Angeles, California, USA
- B.T. Jacobson
RadiaBeam, Santa Monica, USA
|
|
| |
Funding: DARPA
The imaging of extremely small, sub-5 micron, transverse beam spot sizes has been a priority in accelerator physics. Here we propose a scheme to generate and image a beam spot size about 1 micron at PEGASUS laboratory at UCLA. We are preparing a 0.8 mm, 1 pC, 10 MeV electron beam to be sent through a permanent magnet quadrupole (PMQ) triplet of strength 130 T/m, focusing the beam to a waist 1.5 microns and a total focal length of 4.5 mm. We use a YAG screen at the beam waist and a mirror to direct optical (520 nm green) light into a Schwarzschild microscope to collimate the light. We will then image the beam using a CCD camera outside of the beam line.
|
|
|
Slides TUOBB4 [45.484 MB]
|
|
| |
| TUPAC29 |
Modeling Space Charge Effects in Optical Bunchers |
511 |
| |
- L.V. Ho, J.P. Duris, R.K. Li, P. Musumeci
UCLA, Los Angeles, California, USA
|
|
| |
Funding: DOE grant DE-FG02-92ER40693
This paper introduces a 1-D, self-consistent simulation of Inverse Free Electron Laser (IFEL) based optical bunchers. Starting with a review of the conventional (monochromatic) IFEL bunching, we consider slow amplitude variation and multiple harmonics of the fundamental radiation wave. We model two new bunching schemes – the adiabatic and harmonic microbuncher and compare the bunching mechanisms between the optical bunchers as well as space charge effects to the modified IFEL interaction. Here, we present a model approximating the space charge fields and verification of the simulation with the well-known Free Electron Laser (FEL) simulator, Genesis 1.3.
|
|
| |
| TUPMA16 |
High Capture Low Energy Spread Inverse Free Electron Laser Accelerator |
619 |
| |
- J.P. Duris, R.K. Li, P. Musumeci, E.W. Threlkeld
UCLA, Los Angeles, California, USA
|
|
| |
Funding: This work was supported by DOE grant DE-FG02-92ER40693, Defense of Threat Reduction Agency award HDTRA1-10-1-0073, and University of California Office of the President award 09-LR-04-117055-MUSP.
We present the design and construction of a strongly period-, field-, and gap-tapered helical undulator for use in a high-gradient, high-efficiency helical IFEL experiment at Brookhaven ATF. The undulator design achieves efficient acceleration without prebunching by matching the ponderomotive and resonant energy gradients along the length of the interaction for the measured laser parameters. Simulations based on the measured undulator fields and experimental parameters suggest that as much as 43 % of a 50 MeV beam will be accelerated to 94 MeV with 2.3 % rms energy spread.
|
|
| |
| TUPSM03 |
10s Femtosecond Bunch Length Measurement Based on Coherent Transition Radiation |
631 |
| |
- X.H. Lu, W.-H. Huang, C.-X. Tang
TUB, Beijing, People's Republic of China
- R.K. Li, P. Musumeci, K.G. Roberts, H.L. To
UCLA, Los Angeles, California, USA
|
|
| |
In this paper, we discuss bunch length measurement based on coherent transition radiation for 10s femtosecond electron bunches with of several MeV energy and several pC charge. The ultrashort bunch length is obtained by velocity bunching using a compact dual slot resonantly coupled linac located after an RF photoinjector. Strong focusing with a solenoid is required to enhance the radiation generation. Filters are used to reconstruct coherent transition radiation spectrum. The transverse and longitudinal form factors are also studied with simulation.
|
|
| |
THOAA1 |
Single-Shot Ultrafast Electron Microscopy |
|
| |
- R.K. Li, P. Musumeci
UCLA, Los Angeles, California, USA
|
|
| |
Electron microscopy is an extremely powerful tool for a variety of studies in physics, biology, material science, and industrial applications. One of the mostly desired capabilities of a future electron microscopy is the improved resolving power in the time domain approaching ps or even fs levels. In this paper we show that the low emittance, low energy spread electron beams from a state-of-the-art photoinjector can be used to take single-shot intensity-contrast snapshots of the sample. The spatial-temporal resolution can achieve 10 nm – 1 ps level. The beam optics is based on permanent quadrupole magnets which are compact and avoid the high charge density cross-over in contrast to solenoids. The proposed single-shot ultrafast electron microscopy will greatly facilitate the studies of irreversible dynamic process in materials.
|
|
|
|
Slides THOAA1 [4.613 MB]
|
|
| |
| THPAC32 |
Transverse Beam Profile Diagnostic Using Fiber Optic Array |
1205 |
| |
- S. Wu, R.B. Agustsson, G. Andonian, T.J. Campese, A.Y. Murokh
RadiaBeam, Santa Monica, USA
- M.G. Fedurin, K. Kusche, R. Malone, C. Swinson
BNL, Upton, Long Island, New York, USA
- R.K. Li
UCLA, Los Angeles, California, USA
|
|
| |
Funding: This work is supported by U.S. D.O.E Contract Number DE-SC0000870
The fiber-mesh diagnostic (FMD) is a transverse beam profile diagnostic based on the emission and detection of Cherenkov radiation produced as a relativistic electron beam traverses through an ordered bundle of fiber optics (SiO2), arranged in a hexagonal close-pack configuration. Sub-10μm transverse beam profile resolution is attainable due to fiber optic core concentricity. Adequate SNR is achieved using a standard CCD sensor. A fiber optic taper input maximizes light collection efficiency by coupling each output channel to approximately single-pixel pitch. A v-groove holder and assembly process was developed to hold many fiber layers in the desired configuration. In this paper, we present results from a fully functional FMD prototype evaluated at the BNL ATF facility that demonstrates the efficacy of this diagnostic.
|
|
| |
| THPAC37 |
Surface Plasmon Resonance Enhanced Multiphoton Emission from Metallic Cathode |
1220 |
| |
- H.L. To, G. Andonian, R.K. Li, P. Musumeci
UCLA, Los Angeles, USA
- G. Andonian
RadiaBeam, Marina del Rey, USA
|
|
| |
We investigate the effect of surface plasmonic optical field enhancement on multiphoton emission from a metallic photocathode. In a previous experiment *, two orders of magnitude increase in charge yield was obtained using a slightly off resonance nanohole array plasmonic structure. In a new attempt, a nanohole structure will be fabricated, using focused ion beam milling, such that the resonance wavelength is at 800 nm, the central wavelength of the photoinjector driver laser pulse. The charge yield is expected to increase dramatically compared to the charge yield from previous nanostructure. We will also present optical characterization of the nanostructures as well the beam characteristics (intrinsic emittance and bunch length) from this nanostructured photocathode.
* Li et al., PRL 2013.
|
|
| |