Achievements Status Issues Comments. in an attempt to contribute to the WG M3, responding to the charges, given by the Snowmass 2001 Org.

Transcription

1 July 3, 2001 Snowmass JLC-C and JLC-X The Schemes Achievements Status Issues Comments in an attempt to contribute to the WG M3, responding to the charges, given by the Snowmass 2001 Org. Committee Nobu Toge KEK Japan

2 JLC-X Main, main linac scheme collab. with SLAC w. BINP, Protvino w. Many Japanese industry JLC-C Back-up main linac scheme collab. with PAL (Korea) w. Many Japanese industry Here, I will NOT repeat Japanese HEPC, ACFA... statements, KEK-SLAC MOU. We go straight into the R/D subjects.

3 2nd Bunch Compressor Pre-Linac Pre-Damping Ring Positron Main Linac Electron Main Linac Collimation / Final Focus Final Focus / Collimation 2nd Bunch Compressor 1st Bunch Compressor Detector Facility Spin Rotator 1st Bunch Compressor Damping Ring Damping Ring Pre-Linac Electron Linac Positron Production Target Electron Gun Spin Rotator Electron Gun

4 Accelerator Test Facility for JLC Beam Diagnostics Wire scanner beam size monitor Water cooling & Air condition facility double kicker extraction 1.54 GeV Damping ring 53.4m Water cooling & Air condition facility Modulator 27.6m Magnet power supply 50.4m Control room Klystron 714MHz RF source Damped cavity Wiggler magnet L0 L1 L2 L3 L4 Lec1 L5 L6 L7 L8 L9 L10 L11 L12 Lec2 L13 L14 L15 L16 Thermionic Gun 80MeV Preinjector DC power supply for modulator 1.54GeV S-band LINAC 120m JLC-ATF, Mar '98 H. Hayano

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6 Target Value Achieved Value Comment Single Bunch Intensity Normalized Emittance Horizontal Vertical Single Bunch Energy Spread[%] Total Intensity with multi-bunch Normalized Emittance Horizontal Vertical 2x10 10 electrons/bunch <5.0 µmrad <30 nmrad 1.2x10 10 electrons/bunch µmrad nmrad < Bunch Length [mm] <6 6 to 8 20x10 10 electrons/train <5.0 µmrad <30 nmrad 4.5 x10 10 electrons/train µmrad 62 to 113 nmrad Measured by DCCT in the Ring. Single Bunch Operation Measured by W-wires at the Extraction line. 35 nmrad has been measured in the Ring. Measured by thin screen monitor at the Extraction line. Measured by Streak Camera Measured by DCCT in the Ring. Multi-bunch Operation Measured by W-wires at the Extraction line. 95 nmrad has been measured in the Ring.

7 DR beam emittance measurement SR interference monitor for both X, Y size vertical size measurement still unstable ( vibration, mirror contamination etc.) Laser wire scanner for Y size only commissioned successfully Extracted beam Energy spread meas. by screen monitor good measure of coupling Tungsten wire scanner 5 wire scanner phase space fit dispersion contribution is large OTR profile monitor (SLAC) commissioned successfully 2/27/01 Hayano

8 SR interference monitor (X) 2nd Mirror 5375 Double Slit Mirror 6045 f=600mm Lens Polarization filter CCD Camera x5 magnifier Lens Band Pass Filter 500nm SR interference monitor (Y) Mirror 1st Lens 2nd Lens Streak Camera Bending Magnet 0 Source Point 2010 SR Source Point Mirror Mirror 1st Mirror Bending Radius 5.73m 2nd SR port Electron Beam SR monitor optics set-up 2nd SR port in Oct. 2000

9 Layout of the SR-interferometer Synchrtron light Polarizer Band pass filter Double slit Lens f=600mm CCD a D y 7m L 0 L 1.3m Interferogram T.Naito I = aj 0 {1+ exp[ ( 2 Da L 0 ) 2 ] cos( 2 Dy L )}

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12 Wire Scanner Wire mount moving direction 45deg beam 10 degree wire µm Tungsten wire 10µm Tungsten wire 0.5µm-step stepping moter stage 0.5µm resolution digital scale

13 10 4 Normalized beam emittance in Linear Colliders SLC Vertical Emittance [nrad-m] ATF JLC/NLC CLIC1000 TESLA(500) CLIC3000 CLIC500 TESLA(800) Horizontal Emittance [µrad-m]

14 Plans of ATF 2001 Understand single bunch vertical emittance reason of vertical emittance growth vacuum level? beam loss at extraction? dispersion contamination at Ext wire scanner? Move to multibunch operation and develop low emittance multibunch find the reason of vertical emittance growth Develop multibunch Instrumentation MB-BPM, MB-wirescanner, MB-Laser Wire R&D of RF-gun For more stable & high current DR injection ( low beam loss in Linac & BT ) 2/27/01 Hayano

15 JLC-C C-band = 5.6 GHz Eacc ~ 35 MV/m Modulator: 350 kv 2.6 µs, Eff = 52.4 % achieved. New model with Eff > 60 % in development. Klystron: Solenoid focussing type - 50 MW, 2.5 µs, 5 0Hz. 3 tubes so far. #2 model running > 3000 hrs. All successful PPM focussing type - First model built and tested in Second model to be built in RF pulse compression: Disk-loaded SLED (SLED-III) Gain = 3.25, Eff = 65 % in cold model. High-power model under development. Accelerating Structure Choke-mode-type for superior HOM suppression Encouraging results at SLAC SSET testing. High-power testing required.

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24 Comments on the JLC-C option Personal view of N.Toge 1. JLC-C is a relatively straightforward (if not trivial) extrapolation fromthe conventional S-band technology. 2. Eacc ~ MV/m appears reasonably solid from the results of the past R/D. Demonstration of such beam operation is the highest priority item. Progress is paced by the funding, not by fundamental technical problems. Perhaps need yrs in the constraints of funding reality. 3. For an LC, with Eacc = MV/m, reaching ECM ~ GeV looks to be a solid promise. ECM ~ GeV looks to be within a reach. P_AC could be an issue. 4. Expected Lumi might be an issue in terms of its competitiveness w.r.t. TESLA and/or new JLC-X/NLC, unless the old '97 table gets updated. Some exploratory work under way, by introducing shorter S_b, longer S_b x N_b, tighter emittance budget. Reoptimization to be done in 3-6 months. 5. Plug-and-play inter-exchangeability of C-band RF/ACC units with X-band RF/ACC units could be worth exploring. That is, in terms of fast turn-on of an copperbased LC. How critical this turns out to be, would depend on the real start-up timing of the LC project. Evaluation within 6 month -1 yr, depending on the priority.

25 JLC-X X-band = GHz Eacc ~ 55 MV/m Beam acceleration and beam-loading compensation already demonstrated (somewhat in a limited scope) in past at NLCTA (SLAC) NLC collaboration in US. KEK-SLAC R&D collaboration (ISG) since Modulator: SLAC / KEK parallel efforts Study semiconductor switches. Klystron: KEK / SLAC parallel efforts PPM focussing type is the R/D focus. RF pulse compression SLAC / KEK joint effort DLDS (Delay Line Distribution System) Superior eff. Numerous low-power testing gave encouraging results. Accelerating Structures: KEK / SLAC joint effort Damped-Detuned structure with rounded corners (RDDS) Precision maching + assy technology at hand. Wakefield meas (ASSET@SLAC) agree with calc. Stability issue in high Eacc operation > 50 MV/m is the main issue current under investigation.

26 In case of ECM = 500 GeV # of klystrons / linac 1656 # of modulators / linac 1656 / N # of acc. structures / linac 2484 # of 8-klys + 12-struc packages / linac 207 # of 72-klys "super RF clusters" / linac 23 9 x 8 Klystrons Beam direction ~ 55m Accelerating Structures Klystron and DLDS Params Peak power 75 MW Pulse length 1.5 µs Perveance 0.8 µp Klys beam voltage kv RF system eff. 0.7 x 0.65 x > 38 % (ultimate) Structure Params Struc length 1.8 m a/λ 0.18 Shunt impedance 90 MΩ/m Q 7800 Grad (NL) 72 MV/m Grad (w.beam) 56 MV/m Active linac length 4.3 km

27 ~ 1.5 µs Modulator pulse Klystron RF drive (also, output) Time #1 #2 #3 #4 Time-slicing of the RF pulse and distribution to accelerating structures by DLDS. 360 ns + switch time Pulsed RF power, delivered to each accelerating structure cluster 1.5 nc x 95 x 2.8 ns, i.e. 260 ns Bunch train Filling time = ~ 103 ns

28 SCHEMATICS OF THE IGBT-BASED KLYSTRON MODULATOR (KEK-Mitsubishi) 25kV Switch unit 50kV 2650A 25kV Switch unit Two 75 MW PPM Klystrons Step-up Inverter 25kV Switch unit 2.5kV IGBT Switch 50kV 2650A Pulse Transformer 1:5 Klystron Output Pulse 500 kv 530 A 1.5 µs Flat-top 2.5kV IGBT Switch Main Output Pulse Waveform Compensation Circuit Compensation Output Pulse Waveform

29 IGBT-Based Modulator: Test Results 7 Output Voltage Output Voltage(kV) Gate Voltage(IGBT, 1st stage) Gate Volatge(V) Time(ns)

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31 Performances f o the PPM-1 and PPM-1.5klystrons. PPM-1 PPM-1.5 Peak power tested (MW) Efficiency (%) 47% 49.6 Pulse length (ms) 1.5 (at 56MW) Micro-perveance 0.79 Latest measurement results of performance of the PPM-2 klystron (June 6, 2001) Design Achieved Peak power (MW) Efficiency (%) Pulse length (ms) (@70MW) 1.4 (@73.2MW) Micro-perveance Repetition rate (pps)

32 73MW Output Power, 1.4µs Pulse Length and 54% Efficiency Ouptut Power (MW) Figure 4. Output Power (MW) Beam Voltage (kv) Time (µs) Beam Voltage (kv)

33 X-Band Main Linac Unit Modulator 500kV 1.5µs Hz Klystrons 75MW 1.5µs Hz Wall plug 100V 50Hz 600MW 400ns TE02 mode extractor Waveguide (φ4.75inch) Load Super hybrid 200MW 75MV/m 1/3 tap-off RF structure 1/2 tap-off DLDS TE01-TE02 mode launcher 600MW 800ns each 55 m 55 m 55 m

34 Mode Launcher Transport Line, 55 meter of circular waveguide that has a diameter of cm diameter Mode Analyzer Multi-mode Load Low Noise Amplifier 54 meter of WR90 Rectangular waveguide All Connections are made with a phase and amplitude stable cables 8514A S-Parameter Test Set HP 8510C Display/Processor HP 8510C IF Detector HP 8510 System Bus Sweep In Stop Sweep Test Set RF Input HP 8350 Sweep Oscillator 20-dB Directional Coupler 1-Watt Amplifier GPIB This PC controls both the network analyzer and the mode analyzer. It is also used for data acquisition PC (Pentium based)

35 TE01 Mode Electric Field Vectors TE02 Mode Electric Field Vectors TE12 Mode Electric Field Vectors

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37 w OD φ 80 OD φ 61 2b 2b OD φ 61 2b p p p t 2a t 2a 2a DS DDS RDDS

38 12 10 R [mm] 8 6 Design Contour +/ 1 µm Design Contour Z [mm] Measurement

39 Average width of 3mm-slit [mm] (A) CMM Disk number OD_ave. [micron] Microsense Meas. (B) 2 Capacitive Gauge Disk number 5 (C) 5 (D) "2a" error [micron] CMM "2b" error [micron] del_2b_a [mm] corr. FF del_2b_a' [mm] corr. FF CMM Disk number Disk number

40 2300(V-Block length) Mirrors Movable stage for capacitive sensors Laser or Autocollimator Rotatable support for the V-block

41 1300 springs stacked disks ~ 2500 weight 1300

42 60 Observed disk-to-disk stacking error (transverse) DDS3 Stacking Data Count M1(i) - M1(i-1) [micron]

43 "Bookshelving" Error During RDDS1 Stacking Measurement done with an autocollimator 50 0 Inclination [sec] Horizontal [sec] Vertical [sec] 1 sec = 5 microradian Disk Number

44 Schematic Diagram of Wakefield Measurement at SLAC ASSET e- NRTL Quadrupole + BPM e+ Dump e+ SRTL DDS e- 3 m

45 10 2 Wake Amplitude (V/pC/m/mm) ASSET Calc w. known errors Calc w/o errors SQRT[Time(ns)]

46 Figure 5. Processing History of Several Accelerator Structure (X-band) 70 MV/m (A) (B) (C) (D) Time with RF On at 60 Hz (hours) 1.8 m long with 12% vg 0.5 m long with 5% v g 1.0 m long with 5% v g 0.5 m long with 3% vg Unloaded Gradient (MV/m)

47 Comments on JLC-X (+ NLC) Personal view by N.Toge 1. The X-band scheme has been a rather ambitious extrapolation from the S-band case, but we have seen by now many reasons to believe that it should be doable. 2. The highest priority issue continues to be demonstration of stable EACC = MV/m (loaded), preferrably with beams, with all the RF components involved at full operational RF power for the order of 1000 hrs or longer. This may take ~ 1 yr (ACC structure R/D) + ~ 2 yr (procure RF sources) hrs But it can be done in stages and in parallel (i.e. JLC-X + NLC) in some aspects. 3. Assuming that Eacc = MV/m (loaded) should be hand, the ECM reach of GeV is fairly solid. ECM exceeding ~ 1 TeV is within a comfortable reach. 4. While "high-lumi" configuration, competitive w.r.t. TESLA TDR, should be feasible, its hardware and operational foundations could invite repeated "re-visiting". 5. Some aspects of technical implementation details and parameters (e.g. DLDS config, RF pulse length,...) need to be sorted out between JLC-X and NLC groups. Likewise, some R/D strategies.