NIX-Note 5 SAC November, 1994 R. Ruth

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1 NIX-Note 5 SAC November, 1994 R. Ruth

2 NLCTA Contributors R.D. Ruth C. Adolphsen R. Atkinson K.L. Bane R.F. Boyce D.L. Burke R.S. Callin G. Caryotakis R.L. Cassel S.L. Clark C. Cofvin T. Dean H. Deruyter R.A. Early K.R. Eppley K. Fant C. Foundoulis R.W. Fuller L. Giannini L. Godshall S.A. Heifets Y. Higashi T. Higo H.A. Hoag D. Hopkins R. Humphrey K. Kendall S. Khelfets K. Ko R.F. Koontz NM. Kroll K. Kubo T.L. Lavi ne T. Lee M. Litynski G.A. Loew A. Menegat R.H. Miller T. Montagne H.W. Moshammer C. Nantlsta E. Nelson v. Nesterov C.K. Ng E.Patet8on. C. Pearson R.M. Phlllips T. Raubenheimer J. Rifkin P. qodrlguez J. Scott J. Spencer S.G. Tantawi K.A. Thompson A.E. Vlieks V. Vylet J.W. Wang P.B. Wilson E.L. Wright A.D. Yeremian A. Young B. Youngman

3 c

4 Compressor E-z J/a 60 l+tev.... _ _I :y.;.....:: Pre-Accelerator t Main Linac Beam Dump 7 Final Focus Electron Source 0 Ir e :.. Positron Source I. : Damping Ring 8I e+ -.,...&. ;:., 7 Compressor.. Pre-Accelerator 4 $ 7:. t e-.:.ẇ...? $5 Beam Dump Main Linac 7-90 Compressor 4454A96 (Schematic Layout of the Next Linear Collider]

5 i Table 1. NLC Parameters Energy per beam Luminosity Linac length (both linacs) Unloaded accelerating gradient RF frequency Electrons per bunch Bunches Repetition rate Wall-plug power Bunch height at collision Bunch width at collision Bunch length at collision Initial 250 GeV 8 x 1O33 15 km 50 MV/m 11.4 GHz 0.65 x Hz WMW 92 3nm 300 nm 100 pm Upgraded 500 GcV 2 x 1o34 15 km 100 MVlm 11.4 GHz 1.3 x 1o O Hz g#r MW nm 430 nm 100 jrm

6 The NLC Test Accelerator Goals 7 0 consfruct and reliably operate an en mode/ of a section of the NLC high-gra8ient ineered linac. Systems Integration Test Bed for RF System Instrumentation Development TO #est those beam dynamics questions coupled fo acceleration. Multibunch Beam Loading Compensation Multibunch Beam Breakup Field Emission Effects Transverse Accelerator Fields

$_.. :. \, I :y.:.: 3.$ .A..; :... )!I.

7 1..,..m... p! e 4d.: : :..:. :. :. :...: w : : :._.. :. \, I :y.:.: 3.I,..,.... i..,..: 1 _..A..; :... )!I..y:;:::.. zl.. 3,.,:.:.: $.:::;$:;;... II g$$:; :...-. :.. : II f...

8 Table 2. NLCTA RF System Parameters (& vq C bjo Parameter NLCTA Energy Design Upgrade I!i Linac unloaded energy gain 340 MeV 1080 MeV Linac active length 10.8 m 10.8 m. i i I Unloaded accelerating pdient 50 W/m 100 kfv/m Injection enera 90 MeV 90 MeV RF frequency GHz GHz Xumber of klystrons 3 6 I Klystron peak power 30 MU 100 hw Klystron pulse length 1.5 /.fs 1.5 p RF pulse compression power gain Phase advance per cell 2;rr/3 2x13 HOM suppression technique Detuning Detuning

NLCTA Upgrade Capability 1.1 Project Gun --> NLC Average Current. Upgrade --> 90 bunches 1.4 nsec spacing. Space Available. Injector Solenoids --> current overhead.

9 NLCTA Upgrade Capability 1.1 Project Gun --> NLC Average Current. Upgrade --> 90 bunches 1.4 nsec spacing. Space Available. Injector Solenoids --> current overhead. 24 Project Acceleration Gradient = 50 MV/m. Gradient for l/2 TeV NLC 0-s 50 MV/m = NLCTA Gradient Gradient for 1 TeV NLC.w> 100 MV/m Upgrade --> 87 MV/m. Modulators Accept two 75 MW Klystrons

11 NLCV I ❻.. ❻ ॐ❻. --, :;,.,et;,ee. * Bi ❼ I IwI.00~ LOOKINGDOWNSTREAM.

15 I-.~::.z.-k-;.n: ::.: i,;,.. _,...1.,,...,.:..;i;:dE-7 ii.-- : :::~:: :.:: :: ::. :i ipiili~ --;:,~~~~.i, ::. l.:: ::::,::~L,:i-lr :-.:::: ;:D::,; ::::::I;;l::;:rg?+==:= _...: , ~~;,:..:;L. 2.. :~~x:z~j:~~-. L:.si.i:i:. _...i::i9gii;:iiiii:ji~:i:) ::i:..:..:.:::::::-:!:::.~~, :::::I1C:i- :_: *..::~::..-n:.,;:,*.,,::~:~:.1:::: ::. : :il:.:,.,....,.: :::::s:.,:i.:: ::::.:..:.. ::..%,:. :::I :.:,....r...:i::.. : :.:,_.,. :- : ;.: :.: ::i. ::. --:,:i.,,,, I,...,::!:..:.~.:: :,:,, :;<..:.:,....i:- : :r::.~ :,:.:!:i::::::: ;:;.::.r::;,,:~; :,~~liiiiil~.:-:i :~~..;-.-:.-. :,.: ::..., :,.._.._.::.::z:,.:. : ::. -7: :::.. : _....,.,..: ::...,. m+:..... :.;;z., : :;z;:r:i...: i _:I _, il,-;: :,;.:+:l :,:,...,,,.,:! {. _. :..., Z..,... :-.. ii!. :..,.._ L :.:,:.;,;:::;;;,:: ::.: -.:L...:.::.:: ::..:._, _:. : (,.. ;..<: -.::...:..;::.:.: j _i, :,..:. I.

16 . II Mde 3. NLCTA RF System Performance Accelerator Structure NLCTA Energy Design Upgrade Gradient (MV/m) Pulse length (ns) Peak power per feed (MW) Pulse energy per feed (J) Feeds per klystron 2 1 POwer Ikansmission Efficiency Pulse Compression Peak output power (MW) \ Pulse energy (J) Power gain Compression ratio 6 6 Compression efficiency Klystron Peak output power (MW) F@ P* h$h (I Klystron efficiency Modulator Klystrons per modulator 1 2 Peak output power (Mw) Modulator efficiency PFN stored energy (J) AC input power (kw) at 180 pps RF System Net Efkiency

17 I - FREQUENCY-DOMAIN AMLYSIS OF A?GSSIBtE BEAU-WADKMC COWPENSATKON SGHEME I / With Dispwsh Tie (ns)

18 . Table II Summary of RF System Status Now( ) LC 9# NLC/Proposal(3) NLC-II( ) (VW (3/95) P/W (>2000) Klystron Peak Power (MW) Klystron Pulse Length (ps) Klystron EfTiciency Modulator Efficiency , 0.95 Pulse Compression Efficiency (1nc.l. Power Transmission) Net RF Efficiency Notes *Decreases to 9.9% with 2 x 25 kw klystron focus solenoids per 7.2 m module. *+ Decreases to 12.2% with klystron solenoids included. (I) Klystron: demonstrated. Modulator: Cassel simulations of NLCTA mod. give q = 0.55 to 0.70, depending on series inductunce. Pulse compression: based on sum of measured components. (2) Klystron: estimated peformance of XL2 from simulations; parameters for NLCTA. Modulator: same as (1). Pulse compression: assumes improved power transmission efficiency with tuning of line sections between flower petal mode converters. (3) Klystron: Based on simulations of low perveance PPM focused tubes. Modulator: Based on Cassel simula~tion of high-efficiency modulator (SLAGPUB- 3851); efficiency will be demonstrated with operating prototype by LC 95. Pulse compression: assumes further improvements in FP converter. (4) Klystron: grid-switched beam with 95% switching q. Pulse compression: Sstage BPC with loaded delay lines and q = 0.95 per stage. Power transmission: q = 0.94, same a+ (3). If a 25 SLED-II pulse compression system is used, RF ef&iency is 44% and klystron peak power is 135 MW. /.

19 I.-... i Comparison of Linear Collider Parameters Table 3 I Parameter I TESLA I SBLC I NLC(- JLC) I I 5a.m 500/s 500/s IO/(11 uv0.l 40/0.1 s;rzb m/3 =I2 6

VIII. Main Linac RF Svstem 1. Parameters and Specifications WlmN w. a. b. C. 2. RF a. b. C. d. e.

Wa-, K-h-*- ii. Structure Mechanical Design Il.*0 d iii. Vacuum System 1 &yo a, RF Pulse Compression and Power Transmission i.

Prototype Performance iii. Detailed Design and Specifications Pk/rwp. Pulse Modulators Da* %A a i. Requirements ii. Design and Efficiencies iii.

20 VIII. Main Linac RF Svstem 1. Parameters and Specifications WlmN w. a. b. C. 2. RF a. b. C. d. e. System Boundaries System Overview and Performance Parameter List System Design Accelerator Structures i. Theoretical Design and Wake-Fields T. Wa-, K-h-*- ii. Structure Mechanical Design Il.*0 d iii. Vacuum System 1 &yo a, RF Pulse Compression and Power Transmission i. SLED-II System Design and Losses ii. SLED-II Components iii. SLED-II Layout iv. SLED-II Vacuum Klystrons avo i. Klystron Design and Simulations ii. Prototype Performance iii. Detailed Design and Specifications Pk/rwp. Pulse Modulators Da* %A a i. Requirements ii. Design and Efficiencies iii. Prototype Performance &3&s& f Protection Systems RI I(=crods* /&qy i. Structure ii. Klystron iii. Modulator RF Drive and Control i. Low Level RF Drive ii. Phase Manipulation and Feedback iii. RF CwJwiv iii; 13 Yc;b Q-43 b-c. u/; IL ILmh.

21 .. Table I NLC Scenarios NLC-I NLC-II t Center-of-Mass Energy 0.5 TeV 1.0 TeV 1.5 TeV a m C D E.F Active Str. Length (km) Accel. Grad.( ) (MV/m) Unloaded/Loaded so/37 SS/SS 100/74 67/55 NO/74 S4/62 \ C,. No. of 7.2 m Modules ls Particles perbunch (lo] ) o.s Repetition rate (Hz) 1so Bunches per RF Pulse RF Pulse Length (ns) Pulse Comp. System( ) SLED-II SLE$I B;; Bx f BxpsC BPC x5 X8 Pulse Comp. Pwr. Gainf3) Kly. Pulse Length (ps) s s Kly. Peak Power(4) (MW) 4s 2 x PFN Stored Energy (J) per Module( ) Net RF Sys. Efficiency( ) Wall Plug Power (MW) (1) Threshold gradient for dark current capture is 61 MV/m. (2) If a X5SLED-Ii system is used for - C, D, E aud F, the klystron peak powers become: 193 MW, 85 MW, 193 MW and 135 MW repectively. The net rf system &ciency is reduced from 50% to 44% and the wail plug powers become: 162 MW, 106 MW, 241 MW aud 204 M-W. (3) Includes allowance for power transmi&od loss. (4) Assumes 2 klystrons per 7.2 m module. (5) Fgr cases C through F (grid-switched )tlystron) this is the switched v assuming 2-l/2% switching loss. It is assumed that storage element (containing perhaps 5 times switched energy) is charged with 2-l/2% loss from AC line. (6) Case B zwumes NLGI efficiencies for klystron and pulse compression.

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23 NLCTA Project Milestones Date 4/ l/ / /94 8/ / /95 2/ / $196 pvlilestone Project conceived First project review NEPA approval Conceptual Design Report complete 1.8-m structure prototype tests complete Klystron prototype complete Preliminary Safety Analysis Document (PSAD) complete SLED-II prototype tests complete Beamline complete to dump Control System required for Injector complete Injector RF System complete Commission Injector, Test beam to end of spectrometer Final Safety Analysis Document (FSAD) complete Accelerator Readiness Review (ARR) complete Linac RF System complete Beam Accelerated to Dump Project complete

24 /, WAKEFIELD MEASUREMENTS I 1) Fix Vertical Drive Bunch Offset: yd = 2.2 mm 2) Vary Relative Bunch Time Separation, t 3) h&sure witness Bunch Deflection: A$ = wl(t) yd A z-e z EM40-E 6 I- E2 3 g 0 G o-- 2 o- s" \ >,a o- '; -I O I 1 I I I -40 I t (PSI t (ps) 80

25 0

26 :o.o I X-BAND stiwcture I Data direct,ion - \ Data direction -

Accelhation Structure SETup (ASSET) in the SLC Test Structure -3mt Beginning of the Second Girder in L102 MEASUREMENT OF THE BUNCH-TO-BUNCH TRANSVERSE WAKEFIELD COUPLING IN THE I&x STRUCTURE Inject a

27 Accelhation Structure SETup (ASSET) in the SLC Test Structure -3mt Beginning of the Second Girder in L102 MEASUREMENT OF THE BUNCH-TO-BUNCH TRANSVERSE WAKEFIELD COUPLING IN THE I&x STRUCTURE Inject a positron bunch into the linac followed by an electron bunch - the positrons serve as the drive bunch and electrons as the witness bunch. Vary the vertical drive bunch amplitude and measure the betatron amplitude of the witness bunch in the linac after the drive bunch is dumped - the ratio of these amplitudes is proportional to the wakefield coupling. Repeat for different bunch-to-bunch time separations to measure the temporal dependence of the long-range transverse wakefield.

28 ' DSA 602 DlGlTlZlNG SlCNAL ANALYZER dote: 4-MAR-94 time: 22:59:35 660mV ACC IN E 75mV /div ACC I N W trig d KC OUT E d

29 0 m 0

31 c

32 100 2i 0 g 5, IO Q) A Distance Behind Driving Bunch (m)

33 + is Transverse Oscillation Amplitude (normalized ) 0 0 a. A bo id b A io ;. 3

$. 80 \ 3 n t 3 40 z 8-2 0 - - - Constant Gradient Detuned Gaussian - - - Constant impedance 11-92 05. 10. 15.$

34 . 80 \ 3 n t 3 40 z Constant Gradient Detuned Gaussian Constant impedance Distance Along Structrure (m) 7307&J Figure 8. Comparison of accelerating field profiles in a 1.8-m-long accekra&r section for 1CKkMw inpu ; power.

35 Section length Phase advance per cell Iris aperture radius NLCTA Structure Parameters. 1.8 m 2 x m Iris aperture normalized radius Group velocity Filling time, Unloaded time constant v Attenuation parameter Elastance (&Z/Q per unit length) Peak input power/(l.8 m) for 50 MV/m Peak power per feed for 50 MV/m Structure average power dissipation for 50 MV/m, 250~ns pulse length, 180 pps 0.218X-0.149X O.l2c-0.03~ 100 3s s nepers V/PC/m 48.1 MW/m 86.5 MW 1.4 kw/m

36 I - /. DSA 602A DlGlTlZlNG SIGNAL ANALYZER dote: 4-MAR-94 time: 22:39:57 TS08 SLED II TEST 1 ornv./div trig d Rl! i I, SLED, L-J -47.7A ~s 2C3ns/ vl= 250. OLlV v2= 28.05mV Av= 27.8OmV iori;&tol I Previous -ii MOi~ t ~ : I

37 I THE RF STRUCTURE 75 cm accelerator structure tested Ez max = 90 MVIm (Power limited). I.&m NLCTA prototype structure complete. Tested to 55 W/m (Power limited). Wakefields of 1.8m structure measured in ASSET. Cells for 2nd 1.8m structure and two 0.9m injector structures in production. 1.8m structure to be diamond-point finish machined at KEK.

38 RF Pulse Comwession 0 SLED II High Power prototype complete: 33 MW input 154 MW output (75 nsec) 0 Compact Mode Converter test to 150 MW - nsec... used routinely now. 0 SLED II NLCTA prototype being assembled now.

39 h

40 THE KLYSTRON 0 XL 1 Achieved Test Accelerator Specifications: 50MW 1.5~ sec. 0 XL 2,3 are in production 0 NLCTA Plan Use2of3 X11,2,3 Produce 1 additional

41 DSA 602 DIGITIZING SIGNAL ANALYZER date: l-nov-93 time: 15:13:50 XL1 Klystron 44mV r - --T w-f t t._.. pt ---t 1 t $7 c Pout Clrc t i 3-9.elnv 1 /div i Pin=85W i Wg d p.s -+ i t i Pout= 51 MW. Vo=415 kv 10=332 A fo=l1.455 GHz Efficiency=37 %

THE NEXT LINEAR COLLIDER TEST ACCELERATOR: STATUS AND RESULTS * Abstract

SLAC PUB 7246 June 996 THE NEXT LINEAR COLLIDER TEST ACCELERATOR: STATUS AND RESULTS * Ronald D. Ruth, SLAC, Stanford, CA, USA Abstract At SLAC, we are pursuing the design of a Next Linear Collider (NLC)