L. Søby 08/05-2007 1Linac4 BPM and Phase Pickup

LINAC4

Beam Position, Phase and intensity Pick-ups

L. Søby 08/05-2007 2Linac4 BPM and Phase Pickup

Linac4 position, intensity and phase pick-up

Overview

Requirements and constraints

Possible Pick-up types

Low beta effects

Acquisition system

Manpower and costs

Summery

L. Søby 08/05-2007 3Linac4 BPM and Phase Pickup

Overview DTL

DTL tank1 DTL tank2 DTL tank3

BLMBLM

BLM

SEM Grid

Beam Loss Monitor

Beam Current Transformer

Position, Intensity and Phase pick-up

Quadrupole / Dipole

32mm 103mm

Is there a magnet here?

L. Søby 08/05-2007 4Linac4 BPM and Phase Pickup

CCDTL module 1 CCDTL module 2

CCDTL module 3 CCDTL module 4

BLM

BLM

Overview CCDTL 1-4

L. Søby 08/05-2007 5Linac4 BPM and Phase Pickup

CCDTL module 5 CCDTL module 6

CCDTL module 7 CCDTL module 8

BLM

BLM

Overview CCDTL 5-8

L. Søby 08/05-2007 6Linac4 BPM and Phase Pickup

SCL module 1 SCL module 2

SCL module 3 SCL module 4

BLM

Overview SCL

BLM

?

L. Søby 08/05-2007 7Linac4 BPM and Phase Pickup

12 Pick-ups foreseen

Diameter 70mm

Could be of inductive type which also measures current, which would reduce the number of current transformers needed.

Overview HEBT

L. Søby 08/05-2007 8Linac4 BPM and Phase Pickup

Overview

Nb. of Pick-ups

Inner

Diameter [mm]

Available length [mm]

E [MeV]

βComments

DTL 3 20

32

103

750

3 - 40

0.08 - 0.28

1 BPM

1 BPM + 1 dipole

BPM, SEM-grid and BCT

CCDTL 8 28

Min 185

~850

40 - 90

0.28 - 0.41

Available length for magnet and BPM after 1st module.

BPM, SEM-grid and BCT

SCL 8 32

Min ~185

?

90 - 160

0.41 - 0.52

4 BPM’s + magnet after each module

+4 BPM’s inside each module only position is required

HEBT 12 70mm -----160

0.52

L. Søby 08/05-2007 9Linac4 BPM and Phase Pickup

What should be measured

Absolute beam position with respect to an external reference.

Relative beam intensity measured by two consecutive pick-ups. Absolute beam intensity after calibration with BCT.

Absolute beam phase with respect to distributed RF reference.

TOF flight between two pick-ups.

FB = 352MHzbunch= 100ps Int. = 109/bunch Pulse l.= 400us I ave. = 40mA

L. Søby 08/05-2007 10Linac4 BPM and Phase Pickup

Requirements

Position Phase Intensity

Dynamic range

DTL: ± 7mm

CCDTL: ± 10mm

SCL: ± 10mm

HEBT: ± 25mm

Nominal phase advance

± 10º ??4-40mA

Resolution 0.1mm 0.1º 0.5mA

Absolute precision 0.3mm 0.5º 1mA

Relative precision 1% 1% 1%

Time resolution 2us 2us 2us

Vacuum 10-7 Torr, NO bake out will be madeAlignment jigs (on magnets)

L. Søby 08/05-2007 11Linac4 BPM and Phase Pickup

Possible Pick-up types

dt

tdI

cr

RA BLelec )(

2V(t)

Area A

r

Due to the very small longitudinal space only Button pick-ups and Shorted strip lines are possible candidates.

)2

()(4

)(V 0U c

ltItI

Zt BB

elec

beta dependent

L. Søby 08/05-2007 12Linac4 BPM and Phase Pickup

Strip line at low beta

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.50

0.2

0.4

0.6

0.8

11

0

Vu 1( )

0.50.03 1

mml

f

vl

vc

l

c

lSinAI

ZVu

opt

Bopt

B

BsB

6.4210*352

10*3*1.0

2

1

2

1

2)

11(

2

)11

(2

)(2

)(

6

8

Much shorter than free space quarter wave length!!

For vB<< c

(β=0.1)

For max. response

So a decrease of 60% (8dB) of the intensity signal.

-40

-35

-30

-25

-20

-15

-10

-5

0

0 1000 2000 3000 4000MHzdB

Coupler 15 cm long

DTL CCDTL SCL

L. Søby 08/05-2007 13Linac4 BPM and Phase Pickup

Transverse sensitivity at low-β

b

xG

LnLR dB

)sin()1(

)10(

160/

22 )(0145.0)(139.0c

b

c

bG

Schafer theorem

Transverse sensitivity varies with beta and frequency ~3.4→5dB/mm = +20% @400MHz / 3MeV.

Note that the longitudinal extent of the field lines are less, and hence the frequency components are higher, on the beam tube wall closest to the beam. The amplitude of the sum signal does not change!

DTL SCL

L. Søby 08/05-2007 14Linac4 BPM and Phase Pickup

SNS Strip-line pick-up• One end is shorted.• 60 degree electrode angle.

Prototype CCL BPM with Feed thru removed.

Feed ThroughIn mini-conflat

Signal pin

Beam

L. Søby 08/05-2007 15Linac4 BPM and Phase Pickup

SNS BPM Installation & Alignment

• The CCL BPM will be rigidly attached to a quadrupole magnet.

• Up and downstream beam tube will be welded to BPM.

• The quadrupole magnet will have an adjustable kinematic mount.

• An adapter plate will be used to mount the BPM to the magnet.

• One side of the adapter plate will be pinned to the magnet face and the other side of the adapter plate will be pinned to the BPM mounting flange.

• Survey target holes are provided as alignment fiducials.

• Place the BPM within 1 mm and measure accurately (within 0.1 mm) where it is located.

BPM mounting flange

CCL Quadrupole

Adapter plate

BPM

L. Søby 08/05-2007 16Linac4 BPM and Phase Pickup

Linac4 magnet and BPM

96.00

Rot.DN40

DN1653.50

34.00

35.00

DN40

12.6012.60

70.00Beam

115.00

Magnet yoke

34.00

Coil

213.00

At present available space is 185mm? in CCDTL and SCL. 250mm seems necessary

Bellow

L. Søby 08/05-2007 17Linac4 BPM and Phase Pickup

Acquisition system

HYBRID

HIF~50MHZ

ADCSIS3300100MS

352MHz

H+

V-

V+

H-

352MHz

352MHz

H

V

FREQUENCYMULTIPLIERLLRF REF.

LO ~402MHz

2.5MHz

Phasedetector

LO ~402MHz

RF 352MHz REF

VIF~50MHZ

IF~50MHZ

Pos= k()*/+offset

Int.= c*k1()*

= k2*(RF - Beam)

TOF= SPu / *c

= -360*f*SPu/ *c

I

Q

90deg.

LOAnalogue or Digital I/Q down mixing is a better solution

L. Søby 08/05-2007 18Linac4 BPM and Phase Pickup

50 MHz

14-b ADC

14-b ADC

14-b ADC

14-b ADC

GateArray

1x/4x GainControl

Top Input

Bottom Input

Left Input

Right Input

Top I ArrayTop Q Array

Bottom I ArrayBottom Q ArrayLeft I Array

Left I ArrayLeft Q Array

Right I ArrayRight Q Array

AFE DFE

Bergoz Analogue Front end

SNS Acquisition system

SNS Digital Front end with I/Q sampling

40MS/s50MHz

Sample IF at 40 MHz to generate I and Q dataSignal vectors calculated from I and Q

L. Søby 08/05-2007 19Linac4 BPM and Phase Pickup

SNS Acquisition system

BPM DigitalFront end

L. Søby 08/05-2007 20Linac4 BPM and Phase Pickup

Bergoz Analogue Front end

SNS Acquisition system

L. Søby 08/05-2007 21Linac4 BPM and Phase Pickup

BPM AFE Prototype Data Sheet

L. Søby 08/05-2007 22Linac4 BPM and Phase Pickup

SNS Acquisition system

AFEDFEClock multipliernot seen.

PCI

L. Søby 08/05-2007 23Linac4 BPM and Phase Pickup

SNS 1U BPM Processor Chassis

Stand alone, sends data via Ethernet

L. Søby 08/05-2007 24Linac4 BPM and Phase Pickup

Manpower and costs

  Cost FTEy NB Tot. Cost Tot FTEy

Design 20000 0.33 4 80000 1.32

Material 5000 0 36 180000 0

Construction 5000 0.018 36 180000 0.648

Electronics (A + D) 5000 0.036 36 180000 1.296

BI software 0 0.25 1 0 0.25

Installation 1000 0.007 36 36000 0.252

Commissioning 0 0.018 36 0 0.648

Total 656kCHF 4.4

L. Søby 08/05-2007 25Linac4 BPM and Phase Pickup

Summary

Position, Intensity, Phase, TOF and relativistic beta must be computed in front-end.

Buttons or shorted stripline Pick-ups can be used.

Shorted strip line pick-up’s have been intensely studied by SNS and optimized for phase linearity. The SNS designs can easily be adapted to CERN Linac4.

Buttons can be ~ 10mm shorter but are non linear and correction algorithms has to be applied. Low beta transverse sensitivity must be studied.

At least 250mm is needed for magnet and pick-up in CCDTL and SCL.

The acquisition system should include I/Q down mixing for the phase measurement.

Bergoz analogue end exists, which is compatible with SNS digital (PCI) front end.

SNS digital front with rack mount PC fit our needs. Otherwise VME specific card has to be developed.

LF and RF stabilized reference lines are needed for the BPM electronics.