ILC Program discussionM. Ross 21.09.2004

Damping Ring Injection / Extraction Kicker Magnet

1) The TDR Kicker:1) 0.6 mrad (.01Tm), 5GeV, 50 m β, 7e-4 stability, 20 each, many meters

long (kicker ‘achromat’ not possible)2) Counter-fed 50 ohm striplines

2) The ‘conventional’ approach (~SLAC)1) Follow and extend the TDR design2) FET / Hard tube / Saturable Ferrite

3) Alternatives:1) Coherent sum CW standing wave kickers (system) – Gollin / KEK2) Waveguide close to cut-off (system) – Gollin / FNAL3) Pulsed traveling wave RF structures (system) – INFN / Cornell4) Shorted-striplines (just the magnet) – Wille (Dortmund) / SPEARIII5) (Hard tube-based pulsers – Frisch)

Consider the application of this technology at KEK-ATF

Counter-fed Stripline(power fed parallel to beam direction gives no kick unless v_g is low)Rise time depends on travelling wave kicker fill time

DESY Kicker RD

Rummler / Shiltsev / BINP

DESY Kicker RD

ITRP Poster (Obier)

(read µ)

DESY Kicker RD – 2 stripline magnets built

Ongoing RD for XFEL switchyard

ATF Kicker development. (2 programs)Program 1 – Conventional pulse technology extremely fast kicker:

Extract ~ 20 bunches spaced by 330 ns; to be used for testing ILC instrumentation in the ATF extraction line

Replace existing extraction kicker for test

25mm aperture, 20KV, 1.3m kicker is enough to extract (3mrad at 1.3GeV)(500A, 10MW peak)

Six 200 mm long stripline pairs - 12 pulsers ($/¥)

Conventional solid state / planar triode pulser with many counter-fed striplines

Roughly 2x harder than ILC

Uses saturable ferrite ‘shock-line’ technology

Program 2 – long pulse kicker for fast extraction – based on epoxy magnet technology (SLAC DR, ATF injection)

ATF extraction

Existing ATF kicker parameters

1.5 m

Work underway at SLAC / LLNL / BN:

FET pulsersShock-lines (Saturable ferrites)Shorted kicker

Injection/extraction from trailing edge of a train (J. Rogers)

Advantages:

• Bunches are always extracted and injected at the end of a bunch train, so the injection/extraction kickers need only have a fast rise time. The damping ring can be much smaller than the dogbone design.

• Positron bunch production rate is greatly reduced, allowing use of a conventional positron source.

Disadvantage:

An additional small ring is required.

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Injection/extraction from trailing edge of a train (J. Rogers)

• Two rings (one large, one small) share a common RF section.

• As damped bunches are extracted from the large ring to the bunch compressor and main linacs, bunches are injected into the small ring, avoiding RF transients.

• When all of the damped bunches are extracted from the large ring, the small ring is full. A transfer kicker located in the common straight section moves all of the bunches in the small ring as a train to the large ring. This requires a gap before the stored train, which does not appear in the train extracted to the main linac.

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Injection/extraction from trailing edge of a train (J. Rogers)

damping in large ring

extraction to bunch compressor & linac

refill large ring

circumference of small ring

circumference of large ring

time

extraction from large ring

injection to small ring

transfer from small to large ring

Simplified timing example: 3 trains of 3 bunches

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George Gollin, University of Illinois

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INFN Frascati (Alesino…)

Adaptation of the CLIC compression technology

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A New Injection/Extraction Section

• At the injection/extraction point, RF deflectors separate bunches into three separate lines

• Two lines have the bunch spacing required by the kicker• Lines are recombined approximately 200 m later• We have worked out timing issues

– The right bunch must be in the right line at the right time

kicker41

kickerInjection/Extraction

Richard HelmsCornell University

Victoria Linear Collider Conference29 July 2004

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Dortmund Kicker

Keith JobeMay, 1999

Slide #

NLC - The Next Linear Collider Project

NLC Prototype

Keith JobeMay, 1999

Slide #

NLC - The Next Linear Collider Project

Probable cross-section

• the magnet will require a controlled impedance

• water cooling is not allowed in the prototype

• vacuum considerations have not been formally addressed

Keith JobeMay, 1999

Slide #

NLC - The Next Linear Collider Project

9/14/04R. Cassel

With an oscillator generate 15Mhz synchronized with beam. Rectify and extract every fifth pulse ~60nsec switch turn on time and ~60 nsec switch turn off time. Rise & fall time of pulse is ~20nsec with 337nsec between pulses.

Rectifed RF ~15MhzSwitched every 5th pulse

On time ~60nsec off time ~60 nsec

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Rectifed RF switched pulse

9/14/04R. Cassel

“Shock Line” SLC kicker ~38kv into 12.5 ohms. Rise time improvement from ~30nsec to ~ 5 nsec rise time

9/14/04R. Cassel

Extracted pulse and Shock line fits into beam

Single kicker pulse+ Shock line

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Kicker Pulse Beam

9/14/04R. Cassel

Extraction and Injection pulses with beam. Extraction is a half sine wave with shock line. Injection is a half sine wave pulse minus a half sine shock line extraction type pulse.

Two Pulses

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Kicker pulse Beam pulse Injection

Dear Josef,

We think we can make it, subject to any difficult specs. which might emerge (eg very low interpulse noise levels). We have built a FET pulser with a 2ns risetime and an equivalent output of 40kV into 50‡ and this did 60kHz [It was actually 20 channels at 10kV but we can combine outputs to make a large voltage and have taken this approach to 48kV on avalanche units). We have also made other FET pulsers which do multi-MHz bursts. Ionisation is sometimes a bit of an issue with high voltages and high repetition rates. At low rates the ionisation all recombines before the next pulse. As soon as the rate is above around 15kHz the ionisation is still around from the previous shot.

It will be quite big (something like a 6 foot high 19" rack) and a very rough first guess is approx $350k for the first one. This is based upon 500 amps into a 50 ohm load. Into a 100 ohm load would require twice the power and a somewhat bigger device.

Tony Dymoke-Bradshaw(Director)Kentech Instruments Ltd.http://www.kentech.co.uk/Unit 9, Hall Farm Workshops, South Moreton, Didcot, Oxon, OX11 9AG, U.K.

Kicker issues

• Pulser / power source– Stability– Rise time/fall time– Repetition rate (3MHz or 1.6MHz)– ‘achromat’ + feedback/feedforward/active cancellation schemes– Timing rms / voltage rms

• Magnet– Beam Impedance– Field flatness– Match– Optics

• Ring operational schemes– e+

• Auxiliary (pre?) ring