The way to fastand "loss-free" SPS kickers

E. Gaxiola

With contributions from AB-BT-KSL sectionand F. Caspers, T. Kroyer, M. Timmins, J.

Uythoven

Kicker Functional specification:

Fast rise- and fall-time very stable magnetic field pulse Rise-, fall-times: 200 ns to 1.1 μs Flattop ripple: 0.5 to 1% Induction field0.08 to 0.16 T

PS / SPS days – 13/01/2005

Limitations: Ferrite Curie temperature: Beam induced losses Beam impedance: Beam stability Maximum operating voltage Switches Maximum current Ferrite core saturation Bsat

Pulsed power Low impedance travelling wave magnet

Speciality magnets * Vacuum; * High voltage; * High currents

Today’s kicker systems Upgraded thyratron switch

performance Semiconductor components

applications Heat conductance cooling Reduced beam impedance

(longitudinal + transverse)Beam stability?!

Injection MKP 2001

4 batch LHC-type injection Modernisation/upgrade MKP systems #1 to #3

Impedance increase 12.5 Ω 16.7 ΩFaster rise timeImproved flattop ripple

PFN’s upgrade: Pulse fine tuning

2004 Rise time improvements for MKP system #4

2006 Final fine tuning (as was done for MKE)

Extraction MKE LSS4 2003

Magnet cooling for reduced beam induced heating Power semiconductor diode stacks

Increased reliability + lifetime(more cost efficient solution)from LHC MKD kicker generator development

2004 Shortened MKE Generator PFN lengths Optimized rise time PFN front cell adjustments

+ adjustable PFN first coil

Reduced kicker ripple Magnet damping resistors

Optimized fall time Mis-matched TMR values+ Use of SPS transverse feedback system (tested in SPS MD) CNGS double batch extraction practically within specs

The hardware limits of the present MKE kicker system are practically reached

Oct 2003 Step 1:As installed in 2003

0.0

5.0

10.0

15.0

20.0

25.0

Time [us]or%

1 2 3 4

Rise timeFall time

Usable batch timeOvershoot [%]

Kick pulse f lattop ripple [%]Post kick pulse ripple [%]

Subsequent improvement step

Pulse parameter

SPS MKE LSS4 pulse parameters

July 2004 Step 3:Mismatched TMR values

Nov 2004 Step 4:Fine-tuning adjustable PFN firstcoil for each MKE generator

April 2004 Step 2:Adding Magnet Damping Resistors+ PFN front cell adjustments

Tune kicker MKQH Beam impedance reduction Test bench

MKQH kicker magnet withceramic inserts withresistive layer coating

Proof of principle

2004 positive results for beam impedance

Approach I

Not applicable to MKE: Due to significantly increased rise time!

Horizontally: 8.2 sigma SPS beamVertically: 3.2 sigma SPS beam

Alumina plates withmetallic finger strips

Ferrite

High voltage conductor Ground electrode

Alumina profile with

Resistive coating

SPS kicker heating

0

20

40

60

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120

20 30 40 50 60 70 80 90

Average MKE temp measured [ o C ]

Nor

mal

ised

kic

k am

plitu

des

[%]

MKE, p.u. BPH23209MKE, average p.u.'sMKE 16.10.03MKQH, 2003MKQH, 2004

Results MKQH kicker magnet

< 20042004

T*Curie reached at TMKE,reference= 45ºC >90ºC

Rise time 1-99%: 0.6 µs 2.9 µs

Results Impedance Measurements MKQH

Further improvements Studies underway

Capacitive coupling by using metallic finger type strips: Beam impedance reduction Im{Z} and Re{Z} Reduced heating via Re{Z}

2006 Machine implementation on one MKE magnet

(2 cells out of 7 cells)If successful: Possible full 9 MKE fast extraction kicker upgrade LSS4 and LSS6 for 2007 and beyond(in e.g. shutdowns)

Approach II

Horizontally: 8.2 sigma SPS beamVertically: 3.2 sigma SPS beam

Alumina plates withmetallic finger strips

Ferrite

High voltage conductor Ground electrode

Bypass-insert:

Double sided comb structure

Approach IIIStrips Printed Directly on Ferrites

Interdigital comb structure 20mm spacing

surface discharge

Results Impedance MeasurementsSingle Kicker Cell (Approaches II and III)

MKE / MKQH kickers 2004

Lab: Significantly reduced beam impedance! Reduced losses

Next step(s): 2005

Study vacuum high voltage breakdown discharge characteristicsTravelling wave kicker: To be X-checked

2006 SPS tests in LSS6

Summary Very useful knowledge build-up phase ’98 – 2006

New kicker diagnostics were added over the past years. Tests for SPS Complex Application 2003 – 2008

Confirmation of the positive impact of the upgrade of the injectors for LHC

“Old” recuperated equipment Upgraded “modern” performance.

This is only a preliminary summary of the findings.More extended analysis + documentation required.More detailed modelling Compare measurements and simulations. Proven solutions recommendations.CERN at the frontier: bigger and ….

Summary (continued) MKP: Rise time improvements done

Further simulations + tuning to be done Higher reproducibility needed Spare to be finalized with increased diagnostics

MKQH: Useful test-bed with proof of principle,not straight forward applicable to other kickersBeam impedance reduction realized

MKE: Further tests to be done with stripes for voltage holding, vacuum, pulse shape in 2006

beam tests Larger scale applications in 2007 …. 2008 ? If not successful New concept (Alternative new kickers, lots of $ +

my) MKE pulse specs: After lots of modifications (not possible for 2003 tests) now practically at their limit

together with damper practically fulfilling CNGS double batch specs(is damper use the definitive solution?)