1 C. Simon CLIC Instrumentation workshop BPM development @CEA/Irfu C. Simon on behalf of the Saclay’s group CLIC Instrumentation workshop 2 nd - 3 rd June

1C. Simon CLIC Instrumentation workshop

BPM development @CEA/Irfu

C. Simon on behalf of the Saclay’s group

CLIC Instrumentation workshop

2nd - 3rd June 2009

202/06/09 CLIC Instrumentation workshop

Introduction

CEA/Irfu is developing two types of BPMs based on a radiofrequency reentrant cavity:

• The first monitor is developed for the CLIC Test Facility (CTF3) probe beam CALIFES at CERN:

- is operated in single bunch and multi-bunches modes. - single bunch resolution potential < 1 µm

• The other BPM developed for the XFEL (Thirsty of those monitors will be installed in XFEL cryomodules) :

- has an aperture of 78 mm - is designed to work at cryogenic temperature in a clean environment - can get a high resolution and the possibility to perform bunch to bunch measurements.

One prototype is installed in a warm part in the Free electron LASer in Hamburg (FLASH), at DESY.


CALIFES linac

6 BPMs are installed on the CALIFES linac

15 MV/mcompression

17 MV/macceleration

17 MV/macceleration

LIL sections

beam dump

Focusing coils

K

quadrupoles

LaserRF pulse compression

2 x 45 MW

10202525

Profile monitor

Beam position monitor

Steerer

RF gun cavitySpect. magnet RF deflector

SpecificationsEnergy ~ 170 MeVEmittance < 20 .mm.mradCharge per bunch : 0.6 nCEnergy spread: <2%Number of bunches : 1- 32 – 226

Bunch charge (single/multi bunch): 0.6 nC/ 6 nC/NbBunch length (rms) : 0.75psInitial /final bunch spacing :5.3/1.8 ps, 1.6/0.5 mmTrain length: 21 - 150 nsTrain spacing (rep. rate): 5 Hz


Reentrant Part

Reentrant Cavity BPM for CALIFES

Bent coaxial cylinder designed to have:

-a large frequency separation between monopole

and dipole modes

- a low loop exposure to the electric fields

• The cavity is fabricated with titanium and is as compact as possible :

~125 mm length and 18 mm aperture 4 mm gap

Eigen modes

F (MHz) Ql (R/Q)l (Ω) at 5 mm

(R/Q)l (Ω) at 10 mm

Measured Measured Calculated Calculated

Monopole mode

3988 29.76 22.3 22.3

Dipole mode

5983 50.21 1.1 7

Due to mechanical tolerances, dipole mode frequencies are different for each BPMs, 100 MHz IF frequency is, therefore, used so that monitors operate in single and multi-bunch modes.


Signal Processing for CALIFES BPM Hybrids installed close to BPMs in the CLEX

Multiport switches used to have one signal processing electronics to control six BPMs.

Analog electronics with several steps to reject the monopole mode

BPMs in the probe beam linac tunnel

beam positionmonitor 1

x1

x2

y2

y1

180°hybrid

180°

hybrid

phaseshifter

3 dBcombiner

beam positionmonitor 6

x1

x2

y2

y1

180°hybrid

180°

hybrid

3 dBcombiner

.

.

.

6 to 1multiportswitch

phaseshifter

x

y

6 dB

6 dB

18 dBm leak.

18 dBm leak.

Filter 5997 MHz600 MHz BW

0 to 70 dB

0 to 70 dB

18 dBm leak.

Lowpass Filter120 MHz

0 to 70 dB

3 dBsplitter

reference2.891 GHz

14 dBm

RF electronics in the hall

8channel

videoamp

Gv = 10

4channel10 bits2 Gs/sADC

2channel10 bits2 Gs/sADC

DAQ in the hall

control unit

VME Crate

signals for switchesand variable

attenuators control

Ix

Qx

Iy

Qy


RF

LO

II-Q

demodulator

Q

RF

LO

II-Q

demodulator

Q

Lowpass Filter200 MHz


AcqirisDigitizers

Hybrid

couplers

RF electronics used synchronous detection with an I/Q demodulator.


Control Command of BPMs1/Sampling with acqiris boards and readout signals on OASIS

3/Results sent on graphic windows under JAVA and in a file to be used with Matlab

6 BPMs implemented

sincos QI

2/Signal processing: Digital Down Conversion

- raw waveform multiplied by a local oscillator of the same frequency to yield a zero intermediate frequency - real and imaginary parts of each IF are then multiplied by a 60 coefficient, symmetric, finite impulse response (FIR), low pass filter with 40MHz 3dB bandwidth

P

A

Qsin

22 QIA

Beam position

A

Icos


Signals read with Oasis viewer (1)

channels

Good transmission behind the first section


Signals read with Oasis viewer (2)

Visualisation of I/Q signals on the X and Y channels


Cold Reentrant BPM for the XFEL

quadrupole

BPMbellows

HOM absorber

gate valve

XFELX-Ray Free-Electron Laser

Specifications

Single bunch resolution (RMS): 50 µmDrift over 1 hour: 5 µmMax. resolution range: +/- 3 mmReasonable signal range : +/- 10 mmLinearity: 10%

Transverse alignment tol. (RMS): 300 µmCharge dependence : 50 µm


XFELX-Ray Free-Electron LaserCold Reentrant Cavity BPM for the XFEL (1)

Twelve holes of 5 mm diameter drilled at the end of the re-entrant part for a more effective cleaning.

CuBe fingers to put in contact feedthrough and cavity

• 30 reentrant cavity BPMs will be installed in XFEL cryomodules

Eigen modes

F (MHz) Ql (R/Q)l (Ω) at 5 mm

(R/Q)l (Ω) at 10 mm

Measured Measured Calculated Calculated

Monopole mode

1255 23.8 12.9 12.9

Dipole mode 1724 59 0.27 1.15


XFELX-Ray Free-Electron LaserCold Reentrant Cavity BPM for the XFEL (2)

• February 2009, a first prototype was sent to DESY to be installed in a cyomodule test

• Few problems are appeared but were resolved:

• One of flange was re-manufactured

• One of antennae was not in contact with the BPM CuBe contact was therefore moved

• Finally, the prototype was assembled to the quadrupole

• The “cold reentrant BPM” passed leak test and high pressure rinsing


Signal processing for the cold reentrant BPM• Hybrids will be installed in the tunnel

• Signal processing electronics uses a single stage down conversion

XFELX-Ray Free-Electron Laser

• RF front-end electronics based on an PCB with surface mount components

• Digital electronics designed by PSI

BPMs in the linac tunnel

beam positionmonitor

x1

x2

y2

y1

180°hybrid

3 dBcombiner

x

y

Qx

ADC

Digital board

Ix

Qx

Iy

Qy

180°

hybrid

Ix

Qy

Iy

Low passFilter 65 MHz

Low passFilter 65 MHz

PLL

reference10 MHz1 Vpp

RF front-end

Band pass filter1724 MHz

110 MHz BW

Amplifier

Isolator

Isolator

Detector

Isolator

LO

RF

LO

RF

90°hybrid

LO

RF

LO

RF

90°hybrid

Mixer

Mixer

3 dBsplitter

3 dBsplitter

3 dBsplitter

Phaseshifter

VideoAmplifier

Attenuator

Attenuator

control unitTo pilot

attenuators, switchs

PLL

3 dBsplitter

Attenuator

reference10 MHz1 Vpp

3 dBsplitter


110 MHz BW


110 MHz BW


RMS resolution: ~4 µm on the Y channel

~8 µm on the X channel

XFELX-Ray Free-Electron LaserBeam Studies

Good linearity in a range ± 12 mm

with 1 nC and dynamic range +/- 5 mm

Possibility bunch to bunch measurements100 bunches read by the reentrant BPM

Damping time (Cavity): 9.4 ns

Time resolution (Cavity + electronics): ~40 ns

• Beam tests carried out with the room temperature reentrant BPM on the FLASH linac

• Simulated resolution with 1 mm beam offset: < 1 um

20 ns

20 mV

40 ns

IF signal behind Lowpass Filter on

channel Δ


Summary

Reentrant cavity BPM at CALIFES:

• Operated in single and multi-bunches

• Final signal post-processing and interface Java applications are under development and should be tested during the next beam time

• Need beam time to calibrate BPMs and determine resolution

Reentrant cavity BPM for the XFEL:

• First prototype was assembled to the quadrupole for a XFEL cryomodule test

• PCB of the RF front-end Electronics designed to reduce the electronics cost

• Circuit is in the making and we need to test it soon…

Thank you for your attention

Documents

1 C. Simon CLIC Instrumentation workshop BPM development @CEA/Irfu C. Simon on behalf of the Saclay’s group CLIC Instrumentation workshop 2 nd - 3 rd June