LCLS Injector Technical Review

Transcription

1 LCLS Injector Technical Review Stanford Linear Accelerator Center November 3& Review Committee Members: Prof. Patrick O Shea Chair University of Maryland Dr. E. Colby Stanford Linear Accelerator Center Dr. D. Nguyen Los Alamos National Laboratory Prof. T.I. Smith Stanford University

2 LCLS Injector Review Schedule Research Office Building Redwood Room C&D Monday November Overview 8:30-8:45 Greetings from John Galayda; 8:45-9:00 Charge to the Committee M. Reichanadter; 9:00-9:30 Committee Executive Session 9:30-0:00 Overview of the LCLS Injector D. Dowell 0:00-0:30 break& discussion Simulations and Gun Design 0:30 - :5 Injector Simulations C. Limborg :5 - :45 20 Hz Gun and Load Lock J. Schmerge :45 - :00 break for lunch Major Injector Components :00 :30 RF System R. Akre :30 2:5 Specifications for Electron Diagnostics C. Limborg 2:5 2:45 Prototyping at GTF J. Schmerge 2:45 3:00 break Beam Quality Issues 3:00 3:30 Laser Heater Justification Z. Huang 3:30 4:00 Implementation of the Laser Heater J. Welch 4:30 5:00 Expt. Status of Beam Requirements for LCLS D. Dowell 5:00 6:00 Open discussion and Committee meeting Tuesday November Discussion and Closeout 8:00 0:00 Committee Executive Session 0:00 :00 Closeout Session 2

3 Charge to the Committee The Technical Review for the Linac Coherent Light Source (LCLS) Injector will be held at Stanford Linear Accelerator Center (SLAC) on November 3 and The review will cover the LCLS injector performance requirements and will critically assess the proposed design and its ability to meet the injector s performance parameters. The committee is requested to:. Determine if the proposed injector design will meet LCLS performance requirements. 2. Identify and quantify technical issues related to the Injector design 3. Cite any foreseen technical risks to the current design. 4. Cite any overly optimistic expectations or assumptions which require further investigation. 5. Determine if the design and construction plans for the injector are reasonable and make comments and suggestions for improving the current plan. A written report (concise ~2-3 pages) of the committee s findings comments and recommendations is requested. Executive Summary of the LCLS Injector The last kilometer of the SLAC 3-km linac will be used to provide a 0-5 GeV beam for the LCLS. A new off-axis injector will be built at Sector 20 in an existing vault. The injector utilizes an S-band rf gun with a metal photocathode. The laser for exciting the cathode will be in a laser room which will be inside an existing building above the vault. A description of the injector physics design utilizing the new operating point is found in a presentation made at FEL200. A more complete description is given in chapter 6 of the LCLS Conceptual Design Report. However as the presentations in this review will show there has been significant progress in refining the injector design beyond what is given in the CDR. The LCLS Project preliminary schedule shows construction beginning in FY06. However the plan is to build the injector in FY05 as a long-lead procurement project. Thus the Project Engineering Design (PED) for the injector will take place principally in FY03 and FY04. The PED includes some prototyping. Further details of the schedule and prototyping plans are presented in the review The funding schedule for the LCLS will provide only very modest funds for the injector PED in FY03 with the bulk of the injector PED funding in FY04. Some PED work will continue in FY05 during construction. General Description of the LCLS Injector The goal of the LCLS injector is to produce an electron beam bright enough to saturate the SASE x-ray fel within a 00 meter undulator. The injector parameters needed to achieve this are given in Table I. 3

4 Table I. Parameter goals of the LCLS injector Parameter Peak current Charge Normalized transverse emittance projected/slice Rate Energy Energy 35 MeV projected/slice Gun laser timing stability Booster mean rf phase stability Charge stability Bunch length stability Value 00 A 0. nc.2 /.0 µm rms 20 Hz 35 MeV 0. / 0.0 % rms 0.50 ps rms 0. rms 2.0 % rms 5 % rms The injector consists of an rf photocathode gun and two s-band SLAC-sections to give an total beam energy of 35 MeV as shown in the figure below. The photocathode gun produces electrons using a drive laser located in a room located directly above the gun. While an important injector component the drive laser is not a subject of this review and will be reviewed by a separate committee of laser experts on November In order to achieve the challenging parameters given in Table I the injector has been designed to include many new features not found in other injectors. These include:. Cathode load lock and a cathode lab located near the injector. 2. Rf gun with dual rf feeds to minimize field asymmetry. 3. High-resolution energy diagnostics between the gun and the first linac section. 4. Dual rf feeds on the first accelerator section to eliminate time-dependent rf kicks 5. Transverse rf deflecting cavity for direct measurement of the longitudinal phase space and slice emittance. 6. Electro-optical bunch shape diagnostics. 7. Wire scanners for high-resolution minimally intercepting three-screen emittance measurements. 8. High-resolution spectrometer for measuring beam properties at 35 MeV. 9. A laser heater is included to allow a controlled increase in the uncorrelated energy to suppress coherent synchrotron radiation and longitudinal space charge instabilities. These and other details of the injector components and subsystems will be discussed in the review presentations. 4

5 SEA L S SC2 X-Y RF PEN. 2- Cathode Load Lock RF Photocathode Gun Low Energy Diagnostics L O NG B ELLOWS A SSEMBLY SPOOLS F ROM V AL VE TREAT MENT C HAM BER VA CUU MPUM P S E0 FC FC E0 MAGNETIC Spectro. SC X-Y QUAD SC X-Y QUAD MAGNETIC Spectro. SLAC 3-m Accelerator Sections U HV ALL META L G ATE S U HV ALL META L G ATE S PO R CU PINE CATHODE H OLDER PO R CU PINE CATHODE H OLDER CATHODE RF GUN QUADS C M Cav. S2 0' HIGH FC2 0' ACCELERATOR SC ' " EO Diagnostic (Bunch Shape & Timing) NOTES: REVISED NOTES: REVISED T.O. KEY: 2... ETC. ARE SIX SOURCE AREAS ALONG THE DRIFT REGION ETC. ARE POINT-SOURCE LOCATIONS ALONG THE HE BYPASS LINE A B C ARE THE DETECTOR LOCATIONS INSIDE THE LCLS INJECTOR VAULT LINAC COHERENT LIGHT SOURCE MODIFICATION TO LINAC QUADS OTR Shield Wall SC4 0' ACCELERATOR SC5 OTR2 CM3 QE0 QE02 EO2 RF KICKER OTR3 BOSIC A QE03 7' HIGH SC6 5 QE04 QE04 Transverse RF Cavity (Emittance & Energy) Wire Scanner typ. WS0 WS0 OTR4 C 0' HIGH B CONCRETE Pb 2 WS02 OTR5 RAD STOPPER RAD STOPPER Laser Heater Undulator HEATE R DL Bend PEN ' ACCEL 0' ACCEL Fe Fe 2 Fe 3 PEN PEN ' ACCEL 2" TUBE PIC PIC Pb 2 4 SC7 6 WS03 QM0 QM02 B0 QB WS04 B SC9 QM03 8 SC9 QM04 9 OTR8 9 OTR8 9.4 ACCELERATOR HE LE SECTION 20-8A SECTION 20-8B SECTION 20-8C PEP-2 HE/LE BYPASS 0 BEAM STOPPER QE-90 3" TUBE SC8 7 OTR7 B0 B0 QM QM DUMP DUMP SC0 SECTION 2-B BEAM DRIFT SECTION Straight Ahead Spectrometer & Diagnostics The LCLS Injector at Sector 20 5