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Intial synchroscan streak camera imaging at the A0 photoinjector

Description: At the Fermilab A0 photoinjector facility, bunch-length measurements of the laser micropulse and the e-beam micropulse have been done in the past with a single-sweep module of the Hamamatsu C5680 streak camera with an intrinsic shot-to-shot trigger jitter of 10 to 20 ps. We have upgraded the camera system with the synchroscan module tuned to 81.25 MHz to provide synchronous summing capability with less than 1.5-ps FWHM trigger jitter and a phase-locked delay box to provide phase stability of {approx}1 ps over 10s of minutes. This allowed us to measure both the UV laser pulse train at 244 nm and the e-beam via optical transition radiation (OTR). Due to the low electron beam energies and OTR signals, we typically summed over 50 micropulses with 1 nC per micropulse. We also did electron beam bunch length vs. micropulse charge measurements to identify a significant e-beam micropulse elongation from 10 to 30 ps (FWHM) for charges from 1 to 4.6 nC. This effect is attributed to space-charge effects in the PC gun as reproduced by ASTRA calculations. Chromatic temporal dispersion effects in the optics were also characterized and will be reported.
Date: April 1, 2008
Creator: Lumpkin, A. H. & Ruan, J.
Partner: UNT Libraries Government Documents Department

Single-shot electro-optic sampling of coherent transition radiation at the A0 Photoinjector

Description: Future collider applications and present high-gradient laser plasma wakefield accelerators operating with picosecond bunch durations place a higher demand on the time resolution of bunch distribution diagnostics. This demand has led to significant advancements in the field of electro-optic sampling over the past ten years. These methods allow the probing of diagnostic light such as coherent transition radiation or the bunch wakefields with sub-picosecond time resolution. Potential applications in shot-to-shot, non-interceptive diagnostics continue to be pursued for live beam monitoring of collider and pump-probe experiments. Related to our developing work with electro-optic imaging, we present results on single-shot electro-optic sampling of the coherent transition radiation from bunches generated at the A0 photoinjector.
Date: August 1, 2011
Creator: Maxwell, T. J.; Ruan, J.; Piot, P. & Thurman-Keup, R.
Partner: UNT Libraries Government Documents Department

Synchroscan streak camera imaging at a 15-MeV photoinjector with emittance exchange

Description: At the Fermilab A0 photoinjector facility, bunch-length measurements of the laser micropulse and the e-beam micropulse have been done in the past with a fast single-sweep module of the Hamamatsu C5680 streak camera with an intrinsic shot-to-shot trigger jitter of 10 to 20 ps. We have upgraded the camera system with the synchroscan module tuned to 81.25 MHz to provide synchronous summing capability with less than 1.5-ps FWHM trigger jitter and a phase-locked delay box to provide phase stability of {approx}1 ps over 10s of minutes. These steps allowed us to measure both the UV laser pulse train at 263 nm and the e-beam via optical transition radiation (OTR). Due to the low electron beam energies and OTR signals, we typically summed over 50 micropulses with 0.25-1 nC per micropulse. The phase-locked delay box allowed us to assess chromatic temporal effects and instigated another upgrade to an all-mirror input optics barrel. In addition, we added a slow sweep horizontal deflection plug-in unit to provide dual-sweep capability for the streak camera. We report on a series of measurements made during the commissioning of these upgrades including bunch-length and phase effects using the emittance exchange beamline and simultaneous imaging of a UV drive laser component, OTR, and the 800-nm diagnostics laser.
Date: March 1, 2012
Creator: Lumpkin, A.H.; Ruan, J.; Thurman-Keup, R. & /Fermilab
Partner: UNT Libraries Government Documents Department

Laser Timing Jitter Measurements using a Dual-Sweep Streak Camera at the A0 Photoinjector

Description: Excellent phase stability of the drive laser is a critical performance specification of photoinjectors such as Fermilab's A0 photoinjector (A0PI). Previous efforts based on the measurement of the power spectrum of the signal of a fast photodiode illuminated by the mode locked infrared laser pulse component indicated a phase jitter of less than 1.4 ps (technique limited). A recently procured dual sweep plugin unit and existing Hamamatsu C5680 streak camera were used to study the phase stability of the UV laser pulse component. Initial measurements with the synchroscan vertical sweep unit locked to 81.25 MHz showed that the phase slew through the micropulse train and the phase jitter micropulse to micropulse were two key aspects that could be evaluated. The phase slew was much less than 100 fs per micropulse, and the total phase jitter (camera, trigger, and laser) was approximately 300 fs RMS for measurements of 50-micropulse trains. Data on the macropulse phase stability were also obtained. A possible upgrade to achieve better phase stability will be also discussed.
Date: April 30, 2009
Creator: Ruan, J.; Lumpkin, A.H.; Santucci, J.K. & /Fermilab
Partner: UNT Libraries Government Documents Department

Upgrade of the A0 photoinjector laser system for NML accelerator test facility at Fermilab

Description: The current Fermilab A0 Photoinjector laser system includes a seed laser, a flashlamp pumped multipass amplifier cavity, a flashlamp pumped 2-pass amplifier system followed by an Infra-Red (IR) to Ultra-Violet (UV) conversion stage. However the current system can only deliver up to 800 pulses due to the low efficiency of Nd:Glass used inside multi-pass cavity. In this paper we will report the effort to develop a new multi pass cavity based on Nd:YLF crystal end-pumped by diode laser. We will also discuss the foreseen design of the laser system for the NML accelerator test facility at Fermilab.
Date: June 1, 2007
Creator: Ruan, J.; Edwards, H.; Fliller, R.P., III; Santucci, J.K. & /Fermilab
Partner: UNT Libraries Government Documents Department

Transverse emittance and phase space program developed for use at the Fermilab A0 Photoinjector

Description: The Fermilab A0 Photoinjector is a 16 MeV high intensity, high brightness electron linac developed for advanced accelerator R&D. One of the key parameters for the electron beam is the transverse beam emittance. Here we report on a newly developed MATLAB based GUI program used for transverse emittance measurements using the multi-slit technique. This program combines the image acquisition and post-processing tools for determining the transverse phase space parameters with uncertainties. An integral part of accelerator research is a measurement of the beam phase space. Measurements of the transverse phase space can be accomplished by a variety of methods including multiple screens separated by drift spaces, or by sampling phase space via pepper pots or slits. In any case, the measurement of the phase space parameters, in particular the emittance, can be drastically simplified and sped up by automating the measurement in an intuitive fashion utilizing a graphical interface. At the A0 Photoinjector (A0PI), the control system is DOOCS, which originated at DESY. In addition, there is a library for interfacing to MATLAB, a graphically capable numerical analysis package sold by The Mathworks. It is this graphical package which was chosen as the basis for a graphical phase space measurement system due to its combination of analysis and display capabilities.
Date: March 1, 2011
Creator: Thurman-Keup, R.; Johnson, A.S.; Lumpkin, A.H.; Ruan, J. & /Fermilab
Partner: UNT Libraries Government Documents Department

Investigation of possible csr induced energy spread effects with the A0 photoinjector bunch compressor

Description: The bunch compressor of the A0 Photoinjector at Fermilab was removed this past spring to install a transverse to longitudinal emittance exchange experiment. Prior to its removal questions arose about the possibility of observing the effects of Coherent Synchrotron Radiation on the compressed beam. The energy spread of the beam with and without compression was measured to observe any changes. Various beam charges were used to look for square law effects associated with CSR. No direct observation of CSR in the compressor was attempted because the design of the vacuum chamber did not allow it. In this paper we report the results of these experiments and comparison with simulations using ASTRA and CSRTrack. The results are also compared with analytical approximations.
Date: June 1, 2008
Creator: Fliller, R.P., III; Edwards, H.; Kazakevich, G.; Thurman-Keup, R.M.; Ruan, J. & /Fermilab
Partner: UNT Libraries Government Documents Department

Envelope and multi-slit emittance measurements at Fermilab A0 photoinjector and comparison with simulations

Description: Recently we have measured the envelope and the transverse emittance of an 0.85 nC electron beam at the Fermilab A0-Photoinjector facility. The transverse emittance measurement was performed using the multi-slit method. The data have been taken with an unstacked 2.8 ps laser pulse. In this paper we report on these beam measurements and compare the results with the predictions from beam dynamics codes ASTRA and GPT using 3D space charge routines.
Date: June 1, 2007
Creator: Bhat, C.M.; Carneiro, J.-P.; Fliller, R.P.; Kazakevich, G.; Ruan, J.; Santucci, J. et al.
Partner: UNT Libraries Government Documents Department

Start to end simulations of transverse to longitudinal emittance exchange at the A0 photoinjector

Description: Various schemes to exchange the transverse and longitudinal emittance have been proposed. [1][2] One scheme involves a deflecting mode RF cavity between two doglegs to exchange the horizontal and longitudinal emittances. This will produce a complete and uncoupled emittance exchange in the thin cavity limit using first order matrix optics. Various other effects, such as a finite length cavity, can leave the emittances coupled after the exchange and dilute the final emittances. Other effects such as space charge and synchrotron radiation can be investigated through simulations. A transverse to longitudinal exchange experiment using the double dogleg approach is underway at the A0 Photoinjector at Fermilab. In this paper we present start to end simulations of the experiment using various codes to account for space charge and Coherent Synchrotron Radiation effects. The results of these simulations are compared with analytical approximations and preliminary data. The effect on the exchange is also discussed.
Date: June 1, 2008
Creator: Fliller, R.P.; Edwards, H.; Ruan, J.; /Fermilab; Koeth, T. & /Rutgers U., Piscataway
Partner: UNT Libraries Government Documents Department

Conversion of a transverse density modulation into a longitudinal phase space modulation using an emittance exchange technique

Description: We report on an experiment to produce a train of sub-picosecond microbunches using a transverse-to-longitudinal emittance exchange technique. The generation of a modulation on the longitudinal phase space is done by converting an initial horizontal modulation produced using a multislits mask. The preliminary experimental data clearly demonstrate the conversion process. To date only the final energy modulation has been measured. However numerical simulations, in qualitative agreement with the measurements, indicate that the conversion process should also introduce a temporal modulation.
Date: March 1, 2010
Creator: Sun, Y.-E; Piot, P.; Johnson, A.; Lumpkin, A.; Ruan, J. & Thurman-Keup, R.
Partner: UNT Libraries Government Documents Department

Optical transition radiation interferometry for the A0 photoinjector

Description: Optical Transition Radiation Interferometry (OTRI) is a promising diagnostic technique and has been successfully developed and used for investigation of relativistic beams. For mid-energy accelerators the technique is traditionally based on thin polymer films (the first one is being transparent for visible light), which causes beam multiple scattering of about 1 mrad. A disadvantage of those films is unacceptable vacuum properties for photoinjectors and accelerators using superconducting cavities. We have studied the application of thin mica sheets for the OTRI diagnostics at the A0 Photoinjector in comparison with 2.5 {micro}m thick Mylar films. This diagnostic is also applicable for the ILCTA-NML accelerator test facility that is planned at Fermilab. This report discusses the experimental setups of the OTR interferometer for the A0 Photoinjector and presents comparisons of simulations and measurements obtained using Mylar and mica-based interferometers.
Date: June 1, 2008
Creator: Kazakevich, G.; /Novosibirsk, IYF; Edwards, H.; Fliller, R.; Nagaitsev, S.; Ruan, J. et al.
Partner: UNT Libraries Government Documents Department

First observation of the exchange of transverse and longitudinal emittances

Description: An experimental program to demonstrate a novel phase space manipulation in which the horizontal and longitudinal emittances of a particle beam are exchanged has been completed at the Fermilab A0 Photoinjector. A new beamline, consisting of a TM{sub 110} deflecting mode cavity flanked by two horizontally dispersive doglegs has been installed. We report on the first direct observation of transverse and longitudinal emittance exchange: {l_brace}{var_epsilon}{sub x}{sup n}, {var_epsilon}{sub y}{sup n}, {var_epsilon}{sub z}{sup n}{r_brace} = {l_brace} 2.9 {+-} 0.1, 2.4 {+-} 0.1, 13.1 {+-} 1.3{r_brace} {yields} {l_brace}11.3 {+-} 1.1, 2.9 {+-} 0.5, 3.1 {+-} 0.3{r_brace} mm-mrad.
Date: February 1, 2011
Creator: Ruan, J.; Johnson, A.S.; Lumpkin, A.H.; Thurman-Keup, R.; Edwards, H.; Fliller, R.P. et al.
Partner: UNT Libraries Government Documents Department

Experimental Studies on Coherent Synchrotron Radiation at an Emittance Exchange Beamline

Description: One of the goals of the Fermilab A0 photoinjector is to experimentally investigate the transverse to longitudinal emittance exchange (EEX) principle. Coherent synchrotron radiation in the emittance exchange line could limit the performance of the emittance exchanger at short bunch lengths. In this paper, we present experimental and simulation studies of the coherent synchrotron radiation (CSR) in the emittance exchange line at the A0 photoinjector. We report on time-resolved CSR studies using a skew-quadrupole technique. We also demonstrate the advantages of running the EEX with an energy chirped beam.
Date: April 1, 2012
Creator: Thangaraj, J.C.T.; Thurman-Keup, R.; Ruan, J.; Johnson, A.S.; Lumpkin, A.H.; Santucci, J. et al.
Partner: UNT Libraries Government Documents Department

Ugrades of beam diagnostics in support of emittance-exchange experiments at the Fermilab A0 photoinjector

Description: The possibility of using electron beam phase space manipulations to support a free-electron laser accelerator design optimization has motivated our research. An ongoing program demonstrating the exchange of transverse horizontal and longitudinal emittances at the Fermilab A0 photoinjector has benefited recently from the upgrade of several of the key diagnostics stations. Accurate measurements of these properties upstream and downstream of the exchanger beamline are needed. Improvements in the screen resolution term and reduced impact of the optical system's depth-of-focus by using YAG:Ce single crystals normal to the beam direction will be described. The requirement to measure small energy spreads (<10 keV) in the spectrometer and the exchange process which resulted in bunch lengths less than 500 fs led to other diagnostics performance adjustments and upgrades as well. A longitudinal to transverse exchange example is also reported.
Date: January 1, 2011
Creator: Lumpkin, A.H.; Johnson, A.S.; Ruan, J.; Santucci, J.; Sun, Y.-E.; Thurman-Keup, R. et al.
Partner: UNT Libraries Government Documents Department

Near-ideal emittance exchange at the Fermilab Photoinjector

Description: The A0 Photoinjector at Fermilab is presently home to an emittance exchange (EEX) experiment. The emittance exchange beamline consists of a 3.9 GHz normal conducting deflecting mode cavity flanked by two doglegs. Electron bunches with charges of 250 pC and energy of 14.3 MeV are routinely sent through the exchanger. Here we present results of a 1:1 transverse and longitudinal emittance exchange. The advent of synchrotron radiation light sources and free electron lasers (FEL) has been a boon to a wide range of disciplines, resulting in a constantly increasing demand for brighter sources and better resolution. This demand translates to requirements on the properties of the underlying electron beams which produce the light. In particular, one is driven to find ways to precisely manipulate the phase space volume of the beam to optimize it for the desired application. Motivated by the FEL requirement for a small transverse emittance, Cornacchia and Emma developed a transverse/longitudinal emittance exchange concept using a deflecting mode rf cavity located in the dispersive section of a magnetic chicane. This method however, contained residual couplings between the two dimensions, leading Kim to propose a modified version which removed that coupling and resulted in a complete exchange. In this configuration, the deflecting mode cavity is placed between two magnetic doglegs thereby removing the afore-mentioned coupling term. We have used this beamline with upgraded diagnostics to measure a near-ideal 1:1 emittance exchange.
Date: March 1, 2011
Creator: Johnson, A.S.; Ruan, J.; Edwards, H.; Lumpkin, A.H.; Santucci, J.; Thurman-Keup, R. et al.
Partner: UNT Libraries Government Documents Department

Design of an electro-optical sampling experiment at the AWA facility

Description: The free space electro-optical (EO) sampling technique is a powerful tool for analyzing the longitudinal charge density of an ultrashort e-beam. In this paper, we present (1) experimental results for a laser-based mock-up of the EO experiment [1] and (2) a design for a beam-based, single-shot, EO sampling experiment using the e-beam from the Argonne Wakefield Accelerator (AWA) RF photoinjector. For the mock-up, a tabletop terahertz experiment is conducted in the AWA laser room. The mock-up uses an IR beam incident on <110> ZnTe crystal to produce a THz pulse via optical rectification. Detection is based on the cross correlation between the THz field and the probe IR laser field in a second <110> ZnTe crystal.
Date: June 1, 2007
Creator: Ruan, J.; Edwards, H.; Tan, Cheng Yang; Thurman-Keup, R.; Scarpine, V.; /Fermilab et al.
Partner: UNT Libraries Government Documents Department

Spatial resolution limits of YAG:CE powder beam-profile monitors at the Fermilab A0 photoinjector

Description: The A0 photoinjector (A0PI) facility at Fermilab has an ongoing proof-of-principle experiment to demonstrate the exchange of the transverse horizontal and longitudinal emittances. This experiment relies on measurements of the transverse emittances and longitudinal emittance upstream and downstream of the exchanger beamline. At several locations along the accelerator beamline, YAG:Ce powder scintillator screens are used to determine beam size, divergence when the screen is downstream of a set of 50-micron-wide tungsten slits, and energy spread when used in an electron beam spectrometer. We have recently performed direct comparisons of beam image and slit image sizes using both the optical transition radiation (OTR) screens and the YAG:Ce screens. For micropulse charges of 250 pC and with beam energies of 15 MeV, we systematically observed larger beam image sizes with the YAG:Ce screens than with the OTR screens. We deduced a YAG:Ce screen spatial resolution limit of sigma = 140 to 180 microns. This term is large enough relative to the actual beam sizes and slit image sizes to be needed as a correction term subtracted in quadrature.
Date: October 1, 2009
Creator: Lumpkin, A.H.; Johnson, A.S.; Ruan, J.; Santucci, J.; Sun, Y.-E.; Thurman-Keup, R. et al.
Partner: UNT Libraries Government Documents Department

Demonstration of Transverse-to-Longitudinal Emittance Exchange at the Fermilab Photoinjector

Description: Phase space manipulation techniques within two degrees of freedom are foreseen to enhance the performances of next generation accelerators such as high-energy physics colliders and accelerator based light sources. At the Fermilab A0 photoinjector, a proof-of-principle experiment to demonstrate the exchange of the transverse and longitudinal emittances is ongoing. The emittance exchange beamline consists of a 3.9 GHz normal conducting deflecting mode cavity flanked by two doglegs. Electron bunches with charges of 250 pC and energy of 14.3 MeV are routinely sent through the exchanger. In this paper, we report our latest results on the demonstration of emittance exchange obtained with significantly improved beam diagnostics. We also compare our experimental results with a simple numerical model.
Date: May 1, 2010
Creator: Johnson, A.; Ruan, J.; Edwards, H.; Koeth, T.; Lumpkin, A.; Piot, P. et al.
Partner: UNT Libraries Government Documents Department

Demonstration of a real-time interferometer as a bunch-lenght monitor in a high-current electron beam accelerator

Description: A real-time interferometer (RTI) has been developed to monitor the bunch length of an electron beam in an accelerator. The RTI employs spatial autocorrelation, reflective optics, and a fast response pyro-detector array to obtain a real-time autocorrelation trace of the coherent radiation from an electron beam thus providing the possibility of online bunch-length diagnostics. A complete RTI system has been commissioned at the A0 photoinjector facility to measure sub-mm bunches at 13 MeV. Bunch length variation (FWHM) between 0.8 ps (-0.24 mm) and 1.5 ps (-0.45 mm) has been measured and compared with a Martin-Puplett interferometer and a streak camera. The comparisons show that RTI is a viable, complementary bunch length diagnostic for sub-mm electron bunches.
Date: March 1, 2012
Creator: Thangaraj, J.; Thurman-Keup, R.; Ruan, J.; Johnson, A.S.; Lumpkin, A; Santucci, J. et al.
Partner: UNT Libraries Government Documents Department

Subpicosecond electron bunch train production using a phase-space exchange technique

Description: Our recent experimental demonstration of a photoinjector electron bunch train with sub-picosecond structures is reported in this paper. The experiment is accomplished by converting an initially horizontal beam intensity modulation into a longitudinal phase space modulation, via a beamline capable of exchanging phase-space coordinates between the horizontal and longitudinal degrees of freedom. The initial transverse modulation is produced by intercepting the beam with a multislit mask prior to the exchange. We also compare our experimental results with numerical simulations.
Date: March 1, 2011
Creator: Sun, Y.-E.; /Fermilab; Piot, P.; U., /Fermilab /Northern Illinois; Johnson, A.S.; Lumpkin, A.H. et al.
Partner: UNT Libraries Government Documents Department

Transverse-to-longitudinal Emittance-exchange with an Energy Chirped Beam

Description: Emittance exchange has been proposed to increase the performance of free electron lasers by tailoring the phase space of an electron beam. The principle of emittance exchange - where the transverse phase space of the electron beam is exchanged with the longitudinal phase space - has been demonstrated recently at the A0 photoinjector. The experiment used a low charge bunch (250 pC) with no energy chirp. Theory predicts an improvement in the emittance exchange scheme when the incoming beam has an energy chirp imparted on it. The energy chirp helps to overcome the thick lens effect of the deflecting mode cavity and other second order effects that might lead to an incomplete emittance exchange at higher charges. In this work, we report experimental and simulation results from operating the emittance exchange beam line using an energy chirped beam with higher charge (500 pC) at different RF-chirp settings.
Date: May 1, 2012
Creator: Thangaraj, J.; Ruan, J.; Johnson, A.S.; Thurman-Keup, R.; Lumpkin, A.H.; Santucci, J. et al.
Partner: UNT Libraries Government Documents Department