DOE/NSF ILC Review April 4-6, 2006

WBS 2.8/3.8 RF Systems

General Goals:

Develop more reliable and lower cost L-band RF source components for the ILC linacs.

Verify performance goals of the rf system

Chris Adolphsen

ILC Linac RF Unit (1 of ~ 600)

Gradient = 31.5 MV/mBunch Charge = 2e10 eRep Rate = 5 Hz# of Bunches = 2967Bunch Spacing = 337 ns Beam Current = 9.5 mAInput Power = 311 kWFill Time = 565 sTrain Length = 1000 s

(8 Cavities per Cryomodule)

3.8.1 Marx Modulator• Definition of Work Package

– Marx is ACD Alternate Design to BCD Bouncer Modulator

– Motivation: Reduce cost, size and weight, Improve efficiency, eliminate oil from tunnel

• FY06 Program– Demonstrate basic operation with full power

prototype by end FY06. – Begin design of DFM Unit for service in klystron test

stands at SLAC and where needed. – Down-select to ACD when successful.

ILC BaselinePulse Transformer

Modulator

IGBT’s

Marx Generator Modulator

12 kV Marx Cell (1 of 16)

• IGBT switched• No magnetic core• Air cooled (no oil)

Full Modulator(~ 2 m cubed)

150 kW Air-CoolLoad for Testing

Modulator Structure, Backbone, Backplanes

Marx Features• Direct-coupled voltage stack of ten 12-kV cells

producing 140A pk @ 1.5 msec.• Cell can operate with failed components.

– 4/5 redundant solid state output, re-charging switch banks.

• Modulator functions with up to 2 failed drivers– 10 needed, 12 available

• Vernier cells correct flat top to +/-0.5%.– Second stage correction also being studied to approach

+/-0.1% if possible.

• Buck regulators (2) have 4/5 switch redundancy

Development Team• Engineering

– G. Leyh, Lead; Piotr Blum, C. Burkhart, J. Olsen, SLAC– C. Brooksby, E. Cook, Bechtel/LLNL

• Consultants– S. Cohen, LANL– J. Frisch, K. Jobe, SLAC – G. Majumdar, Mitsubishi– H. Pfeffer, FNAL

• Industrial Participants– Diversified Technologies, Bedford MA– ISA, Dublin CA– Stangenes Industries, Palo Alto CA

Prototype Development Schedule

Marx Modulator Status

• Modulator support structure, backbone, complete

• First prototype Marx Cell ready for testing.

• Equipotential rings, connection planes complete

• PPS system for modulator 30% complete• Air cooled 150 kW test load 25% complete

• 12kV single-cell test stand ready for operation

• As of March 1, 2006,– Labor charges = 187 k$ (576 k$ allocated)

– M&S charges = 280 k$ (370 k$ allocated)

3.8.2 SC Linac Quad and BPM• Goals:

– Characterize field properties of a prototype linac SC quad.

– Verify quad center moves < 5 microns when the field strength is changed by 20% as required for beam based alignment.

– Develop cavity BPMs with micron-scale resolution for multi-bunch (200 ns spacing) operation.

• Project Description:

– Acquired a prototype SC linac quad (80 mm bore, cos[2] type) from CIEMAT/DESY. Building a warm-bore cryostat for it at SLAC.

– Characterize quad magnetic field with a rotating coil, in particular, to measure any motion of the magnetic center when the field strength is varied.

– S-band rf cavity bpms have been designed and a triplet built that will be tested with beam in End Station A (ESA).

– BPMs have half the nominal aperture to simplify testing design concept and because it would be advantageous for the ILC.

– In FY07, propose to test quad and bpms with beam to demonstrate required quad shunting performance.

Cos(2) SC Quad(~ 0.7 m long)

S-Band BPM Design(36 mm ID, 126 mm OD)Field Map

Al Cylinder

Iron YokeBlock

SC Coils

He Vessel

ILC Linac SC Quad/BPM Evaluation

He Vessel Support in the Cryostat

Cryostat and Cryogenic System

Series of measurements (8 minutes each) of a 25 cm long NLC prototype quad - shows that sub-micron resolution is possible and systematics are controllable.

Currently designing longer, wider coil for SC Quad test – will qualify it first with a NC Quad.

X C

en

ter

(mic

rons)

Measurement

For Magnetic Center

Measurements,Adapt Apparatus

Developed for NLCNC Quads

S-Band (2.86 GHz) BPM Mode Spectrum (monopole mode signals suppressed geometrically)

BPM Triplet to be Tested with Beam

SC Quad/BPM Status• Magnet received from DESY in January after initial testing there in a

vertical Dewar. Gas-filled leads received in March.

• With help of Tom Nicol at FNAL, developed a low heat loss, stable support

design for the He vessel. May adopt similar support structure for the ILC

linac.

• Cryostat drawings currently being submitted to the SLAC shops.

• First tests of new magnet measuring coil planned during the next month

using a NC quad. SC quad measurements planned for July.

• BPM triplet built and installed on girder in ESA. Beam test to start April 24.

• As of March 1, 2006

– Labor charges – 112 k$ (144 k$ allocated, 240 k$ requested last October)

– M&S charges – 126 k$ (205 k$ allocated, 250 k$ requested last October)

– Project at ~ 50% point with about half of the requested funding spent.

3.8.3 Coupler Development(LLNL / SLAC)

• Goals:

– Understand rf processing limitations (typically takes > 100 hours per coupler).

– Assess effect of coupler coatings, bellows, and widows on processing time.

– Propose changes to TTF3 design to improve performance and lower cost.

• Project Description:

– Eleven coaxial sections (40 mm ID, 70 Ohm) will be prepared that vary in

terms of material (SS or Cu), bellows (none, 5 or 10 folds) and windows (with

and without).

– A general purpose waveguide (WR650) to coax adaptor has been designed to

power the test sections in vacuum.

– Use the L-band rf source that has been configured at NLCTA (currently

produces 3.3 MW, 1 msec pulses at 5 Hz: need only ~ 2 MW).

To understand processing limitations, plan to process coupler components individually. In particular, determine if bellows or the windows are the source of the long processing time.

Concern that the surface field variations in the bellows and near the windows may lead to excessive mulitpacting.

Coupler Processing Studies

Cou

pler

Su

rfac

e F

ield

Coupler Development Status

• Have decided on basic

layout of system to test

coupler parts – drawings

are being prepared

• Setup uses a detachable

center conductor and 50

cm long test sections

• As of March 1, 2006

– 15 k$ labor charges

(180 k$ allocated)

– Zero M&S (100 k$

allocated)

• Ready for first tests this

Summer.

2.8.1 RF System Design• Doing tracking simulations of multipacting in the TTF3 couplers in

conjunction with coupler R&D program. Will produce 3D map of

multipacting 'activity' -vs- rf power and longitudinal position along the

coupler outer surface.

• Studying ways to reduce rf distribution costs: considering three

changes to the basic design:

1. The circulators in the TDR design are a big cost item (~ 35% of total

distribution system). To eliminate them, power the cavities in pairs using

3 dB hybrids, which would still isolate them.

2. Develop a variable tap-off system to feed the cavity pairs.

3. Replace the three-stub tuner with a mechanical squeeze type phase

shifter that would adjusted after the system is setup.

• As of March 1, 2006

– 83 k$ of labor charges (126 k$ allocated)

Multipacting Simulation of TTF3 Coupler

Bellows

Primaries -Green, Secondaries- RedPrimaries -Green, Secondaries- Red

“Cold Side”

With two-level power division and proper phase lengths, reflections from pairs of cavities are directed to loads. Also, fewer types of hybrid couplers are needed in this scheme. There is a small increased risk to klystrons (total reflection from a pair of cavities sends < 0.7% of klystron power back to the klystron.)

Similar to TDR and XFEL scheme.

Baseline RF Distribution System

Alternate RF Distribution System

FY07-09 RF System Program• Goal: demonstrate viable, cost-optimal rf source for ILC. Operate six

‘production’ sources from industrial vendors by FY10. Supply power

source and couplers for RF unit test at FNAL.

• SLAC has substantial expertise in this area and ILC Americas expects

SLAC to lead this program. Would be responsible for all components

from the AC power to the couplers.

• Program would be comparable in size to that during NLC rf

development.

• Schedule meshes well with FNAL cryomodule program.

• Schedule allows for testing to establish > 2000 hour MTBF’s, which is

minimum allowable in particular availability models.

Yale University Beam Physics LaboratoryPROGRESS REPORT

20-MW MAGNICON FOR ILCsupported under DoE grant DE-FG02-05 ER 41394, 9/1/05 – 8/31/08

Program objectives: (a) To provide laboratory infrastructure at Yale needed to allow tests of a 20-MW, 1.3 GHz magnicon amplifier being designed and built to be an alternative RF source for ILC. (b) To coordinate closely with Omega-P, Inc. in its design and fabrication of the 20-MW magnicon, anticipating future tests at Yale.

Funding profile:FY06grant

FY06, to 3/13/06

FY07 budget

FY08 budget

labor 12,788 14,228 13,427 14,098

materials 6,400 6,400 5,873 10,367

equipment 18,000 6,464 22,000 25,000

other + indirect

22,812 17,201 23,700 15,535

totals 60,000 44,293 65,000 65,000

WBS 3.8.4

Progress to date (9/1/05 - 3/21/06)

A. At Yale Beam Physics Lab, room 112 (M.A.LaPointe, J.L.Hirshfield):

1. added 72 kW ac power, to bring total up to 150 kW;

2. relocated water pipes so that shielding door can close ($11k from Yale towards cost);

3. ordered 150 kW heat exchanger.

B. At Omega-P (V.P.Yakovlev, J.L.Hirshfield):

1. refined conceptual design for magnicon;

2. made preliminary simulations for TE111-mode output cavity (reduced RF

surface field in output cavity, compared with TM110-mode and with MBK);

3. began negotiations with potential industrial partner for fabrication of tube

and contribution of 30 MW / 80 kW modulator, suitable for 1.6 ms pulse width, ~1 Hz rep rate operation of 20-MW, 1.3 GHz magnicon.

20-MW, 1.3-GHz MAGNICON AMPLIFIER FOR ILC

Preliminary design layout and design specifications

peak output power 22.5 MW

average output power 180 kW

pulse duration 1.6 ms

repetition rate 5 Hz

efficiency 75%

gain 44 dB

FWHM bandwidth ~ 2 MHz

beam power 30 MW

beam voltage 300 kV

beam current 100 A

beam perveance 0.61 perv

Ribbon-Beam Klystron Research:

Improving Efficiency in High-Power Klystrons

Chiping Chen

Plasma Science and Fusion Center

Massachusetts Institute of Technology

DOE ILC Review

April 5, 2006

33DOE ILC Review Chiping Chen, Intense Beam Theoretical Research Group

WBS 3.8.5

Ribbon-Beam Klystron

• Klystron is a high capital cost, high operating cost item for ILC.

• Ribbon-beam klystron (RBK) is a leading ACD choice, because it is better than the multi-beam klystron (MBK) BCD choice. – Higher efficiency (75% vs. 65%)– Single beam vs. 6 beams– Energy-free permanent magnet vs. energy-consuming

pulsed magnet

• RBK provides potentially the following savings:– Klystron hardware: 66% (or $60M) saving. – RF system electricity: 20% (or $20M/year) saving.

34DOE ILC Review Chiping Chen, Intense Beam Theoretical Research Group

35DOE ILC Review Chiping Chen, Intense Beam Theoretical Research Group

Ribbon Beam Improves Klystron Efficiency

0 1 2 3

Micro-Perveance

0.0

0.2

0.4

0.6

0.8

1.0

Effi

cien

cy SLAC XP3 Klystron

MBK (Multi-Beam Klystron)

RBK (Ribbon-Beam Klystron)

0.8 - 0.2 P

2/36 /10PerveanceMicro VI

Parameter New Design

Freq (GHz) 1.3

RF Power (MW)

10 (pulsed)

Current (A) 111.1

Voltage (kV) 120

S (cm) 2.2

kox/koy 0.158

B0 (kG) 2.0

a/b 20

a (cm) 1.0

max (deg) 0.75

Current Status and Budget

• 2005 Status– Carried out innovative research to successfully reduce

the twist angle of the elliptic beam (2005).– Applied results of ribbon beam physics studies in our

consideration of design options for the ribbon-beam transport system (2005).

– Determined the feasibility of magnet engineering required for focusing the elliptic electron beam (2005).

– Developed a small-signal theory of RBK (2005).

• 2005-2006 Budget– Total Amount Funded: $30K – $5K left

36DOE ILC Review Chiping Chen, Intense Beam Theoretical Research Group

Summary• Have made good progress toward achieving FY06

goals.

• Gaining expertise in low-frequency, long-pulse rf

sources required for ILC, and beam related issues

with SC quads and ‘cold’ BPMs.

• Starting in FY07, will expand work toward producing a

robust klystron and a lower cost rf distribution system.

• In a good position to ramp up program in the next few

years to produce several prototype ILC rf sources.