Slac steve smith may 2009 linac coherent light source at slac lcls injector at 2km point existing linac 1 km near experiment hall far experiment hall undulator m. Use facetii linac to drive a highbrightness plasma injector in facet experimental area. Particularly challenging are the requirements for the electron injector to operate in the ngls, which must deliver beams at mhz repetition rate with the required high brightness over a broad range of charge per bunch. Beam emittance investigation in high brightness injector. The fel radiation output efficiency is often parametrized through the power gain length that relates fel performance to electron beam quality at the undulator. Though the designs of the diagnostics are based largely on technology from synchrotron light sources, the high intensity and high brightness of lcls xray beam are well outside of the range of parameters for synchrotron light sources, so the diagnostics must perform in. An rf gun and laser heater system were installed in an offaxis tunnel to produce a 250pc, beam with a typical normalized emittance of 0. This, especially for fel applications, is taken to mean the 6d brightness of the beam, which is quanti ed by b 6 d q nx ny nz. The lcls ii laser room will be located at the start of the linac at sector 0, which was previously the site of the collider injector cid.
There are three laser beam properties that are probably more important than any other. The constant current value of all 16 channels is set by a single external resistor with 128 steps for the global brightness control bc. Abstract the diamond light source dls is a new medium. Since the uncorrelated local energy spread of electron beams generated from a photocathode rf gun is very small, the microbunching gain may be large enough to significantly amplify rfgun. Recent advances in ultrafast xray sources philosophical. Abstract a high brightness injector has been developing in hls. The uclanicadd plasma density transition trapping experiment. The main bottleneck limiting the beam power in circular machines is caused by space charge effects that produce beam instabilities. A relatively small increase in driver beam charge can compensate for. Kempson, diamond light source, rutherford appleton laboratory, chilton, didcot, oxfordshire ox11 0qx, uk k. This is followed by two sband linac sections, where the beam is accelerated to an energy of 5 mev 17. Xray free electron laser seeded by ir laser driven high.
During the initial lcls commissioning the readings were questionable and an existing. Measurements and simulations of ultralow emittance and. Status of beam commissioning in frib driver linac, t. The results and performance are presented in details. Lcls list of the technical notes series for the lcls project. A series of measurements are performed for low energy beams in the european xfel injector. Methods the initial proposal for hard xray selfseeding at lcls is described in ref. In this design, from these two sources, nit is the most important contributor to the accelerating voltage variation and driver input power. Both noise source are in general random combining noise sources with wideband white 1f and 1fn spectral characteristics. On the importance of electron beam brightness in high gain. Because of the reliability of the magnetic crowbar switch, more than 500 shots were accumulated on the cathode at over 1 kacm2 with no degradation of the output.
High brightness ws, daresbury 2011 xband rf photo injector xband vs sband xband injector performances vs those from lcls injector 250 pc much better emittance h, bunch length 3 20 pc emittance h, bunch length 2 10 pc calculations show very promising for compact xband fel driver. The incorporation of a deltaundulator afterburner in lcls has enabled the generation of circularly polarized xray pulses in the soft xray range between 500 and 1500ev with. From accurate measurement of the laser beam width are derived much more accurate measurements of beam divergence, the m2 or times diffraction limit of the beam, and other important beam properties. Physics and engineering issues of ppi pohang photoinjector. In addition, electronic laser beam diagnostics provides other measurements of the laser properties, such as gaussian fit of near gaussian beams, top. The xray fel process demands very tight tolerances on the straightness of the electron beam trajectory the electron injector for the slac linear coherent light source lcls must produce a low jitter, high brightness beam. The operation of lcls in the low charge mode 20 pc substantially improves the transverse emittance of the e beam from the injector and further mitigates collective effects in the accelerator, allowing for extreme ebunch compression. Scan wire through beam, measure secondary radiation direct calibration. The lcls injector reliably delivered a high quality electron beam since it started operations three years ago. Proposal for a flat beam injector brinkmann, flottmann and derbenev 2000. To increase maximally the beam power of a proton driver, it is proposed to build a facility consisting solely of a 2. Can read individual bunches in a train slightly invasive slow. The site will be refurbished in order to accommodate the new laser lab, along with the beam transport to the rf gun. This note is to summarize what we have understood from the lcls injector including drive laser, cathode, rf gun, injector beam line elements, beam modeling and operations.
Lcls at slac requires the rf photo injector to produce a beam with a normalized, projected emittance of 1 micron in a 10 ps long. Measured circles and predicted squares normalized brightness at the end of the fermi linac as a function of the beam charge. The ideal injector would generate high brightness beams, and accelerate them up to the energy above which the spacecharge forces are reduced to such a level that downstream beam transport and acceleration are done without the loss of the beam brightness. Serafini, homdyn study for the lcls rf photo injector. Each channel can be turned on or off by writing data to an internal register. Commissioning results of the lcls injector dowell, d.
Linear accelerators delivering high brightness electron beams are essential for driving short wavelength, high gain freeelectron lasers fels. The operation of lcls in the low charge mode 20 pc substantially improves the transverse emittance of the ebeam from the injector and further mitigates collective effects in the. Plasma wakefield acceleration experiments at facet ii. Maximum achievable beam brightness from photoinjectors. Oct 22, 2007 various lcls specific issues including beam steering from the xband rf, not of great general interest run uncovered some issues that are of general interest. The lcls freeelectronlaser uses the last 1 km of the 3 km existing linac at slac, in addition to about 800 m of new construction, which houses electron beam transport, the undulator, the diagnostic front end and two experimental halls connected by a 200 m long photon transport tunnel. Once on the axis of the main linac, the lcls electrons are accelerated to 250 mev in three 3m long s band accelerating structures l1s before entering the first bunch compressor chicane bc1. The 4 gev lcls ii superconducting linac with high repetition beam rate enables the possibility to drive an xray fel oscillator at harmonic frequencies. Status of task force efforts slac national accelerator. The tlc5929 is a 16channel constant current sink led driver. Thus, the laser spot size is somewhat larger than the electron spot size, result ing in the doublehorn energy distribution fig.
Linac coherent light source lcls conceptual design report. Lcls at slac requires the rf photoinjector to produce a beam with a normalized, projected emittance of 1. Fel requirements, the lclsii injector must simultaneously deliver high repetition rate up to 1 mhz and high brightness electron beam with normalized emittance of beam requirements for lclsii injector are summarized, as presented in table 1. Serafini, homdyn study for the lcls rf photoinjector, in proceedings of the 2nd icfa advanced. The second of these independent trailingbunch schemes would be to utilize the lcls ii beam that will be present in an overhead beam pipe as it passes through the middle km of the slac tunnel. Decelerating the beam and extracting its energy for use in the acceleration process accomplishes the recovery of the beam energy. A microbunching instability driven by longitudinal space charge, coherent synchrotron radiation, and linac wakefields is studied for the linac coherent light source lcls accelerator system. Beam charge feedback system for thermionic cathode rfgun cathode, feedback, controls. Erls inherit the high peakbrightness of linac, and through energy recovery assume the high efficiency of rings, and therefore are also capable of a high average beam power at high brightness. Beam charge measurement the absolute charge measurement at lcls is designed to be done with a number of toroids distributed at various locations from the injector through the undulator area which then serve as crosscalibration for all the bpm charge measurements. The calculation, simulation, and measurement of longitudinal. Will concentrate on the issues for beam transverse profile monitors.
Travish ucla department of physics and astronomy n. Various lcls specific issues including beam steering from the xband rf, not of great general interest run uncovered some issues that are of general interest. Electron sources for future lightsources, summary and. First experimental measurements of the caustic nature of. Tlc5929 16ch constant current led driver with 7bit. Emittance optimization is an indispensable part in conditioning and operation of the facility. On the control of e beam parameter with laser plasma accelerators v. This 48 gev beam could be diverted at up to 30 hz down into the facet ii portion of the tunnel and doglegged onto the main line of the linac. A high brightness injector was designed niufnal collaboration. Maruta frib thzba3 novel emittance measurement combining foil focusing and pepperpot techniques, k. Given the similarities between the linac coherent light source lcls fel at slac and the fermi photoinjector requirements, this design draws heavily on the lcls concept to produce a 510 ps long pulse with jector is a high brightness electron beam. The compression and charge markers are shifted in the abscissa for better reading. Beam charge feedback system for thermionic cathode rfgun cathode, feedback, controls, electron. Diagnostics for high brightness beams are much more difficult that we had anticipated.
We performed various beam optics measurements to ensure that the conditions for fel operation at flash2 are fulfilled. The injector must simultaneously deliver high repetition rate up to 1 mhz and high beam brightness with normalized emittance of 0. Maximum achievable beam brightness from photoinjectors ivan v. For a laserdriven high brightness injector, different time structure of the laser pulse has different effects on transverse emittance. Measurements of the linac coherent light source laser. Build a second beam line to inject this new beam into the lcls linac to diagnose, prepare and inject into existing undulators.
Design of beam measurement system for high brightness. Slice emittance measurements at the slac gun test facility. Xray free electron laser seeded by ir laser driven high order. High brightness photo injectors for brilliant light sources. Lcls injector to operate simultaneously when a high energy 30 gev beam is being accelerated in the 3km linac. The lcls project modified the last 1 kilometer of the slac high energy physics linac to provide a 15 gev driver for an xray fel. Photon beamlines and diagnostics at lcls sciencedirect. We consider a 3d electron bunch at the cathode, modelled via photoemission, with realistic asymmetric spatial and temporal distributions for accelerator beam dynamics studies at the european xray freeelectron laser european xfel. Slac steve smith may 2009 linac coherent light source at slac lcls injector at 2km point existing linac 1 km near experiment hall far experiment hall undulator m xxxfel based on last 1km of existing linacfel based on last 1fel based on last 1km of existing linac.
Use scintillator material in beam single shot image. Suppression of microbunching instability in the linac. Phase space manipulations of electron beams between two. Piel, accel instrume nts gmbh, bergischgladbach, germany. Barov northern illinois university department of physics h. Highlights of the 47th icfa workshop on the physics and. Berkeley lab working on key components for lclsii xray. These are the total power or energy in the laser beam, the temporal pulse width, and the spatial width of the laser beam. The uclanicadd plasma density transition trapping experiment m. The compression factors are 7, 6, 6 and 12 for beam charge values of 250, 350, 450 and 500 pc respectively. This beam must be accelerated and longitudinally compressed to yield a sub. Lclstype high brightness electron bunch seeded by hhg ultrashort, powerful, hard xray fel. Dec 29, 2011 beam emittance plays an important role in any accelerator, and it is a main parameter to judge the performance of an accelerator. The injector emittance measurements are made using an intercepting 1 m thick aluminum screen otr2 in 1 after acceleration to 5 mev, where the transverse electron beam size is measured using optical transition.
Initial measurements of the bunch length after the beam has traversed approximately 10 meters through the injector show that bunch length is much longer than the initial laser pulse width and also depends on current. An electron gun with carbon nanotube cathode has been installed in the kekbpf linac, and the beam acceleration tests up to 2. Halavanau slac mozba4 high brightness cw electron beams from sc rf photoinjector, i. Some initial commissioning results were described in ref. Hhg seed on lclstype electron beam in lclstype injector accelerator undulator system hhg seed is attractive, being considered by a few. The lcls technical notes series is an lcls internal publication of papers, relevant to the lcls project. Beam measurements at the lcls injector figure 2 presents a schematic of the lcls injector and the first stage of magnetic bunch compressorbc1 regions. Suppression of microbunching instability in the linac coherent. Compared to the regular lcls ii machine setup, the oscillator mode requires a much longer bunch length with a relatively lower current. Measurements and analysis of a highbrightness electron. A specific beam optics in the extraction arc with horizontal beam waists in the bending magnets is mandatory in order to mitigate effects from coherent synchrotron radiation csr. The forwardbragg scattered beamconsists ofaprompttransmitted beam anda delayed. Erls inherit the high peak brightness of linac, and through energy recovery assume the high efficiency of rings, and therefore are also capable of a high average beam power at high brightness. Berkeley lab working on key components for lclsii xray lasers.
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