Beam Line Tuners

f

Beam Line Tuners

Vic Scarpine

Instrumentation

DoE Review

Oct 28-31, 2002

October 28-31, 2002 DoE Review - Instrumentation - BLT 2

f Introduction

• Primary function of a Beam Line Tuner (BLT) is to measure turn-by-turn transverse beam positions during transfers between machines at injection to improve closing– Required in Tevatron, Main injector and Recycler

– Can measure betatron oscillations, fractional tune, coupling, phase, synchrotron oscillations, chromaticities, etc

• Focus has been on betatron measurements for improved closing

– Feed-forward correction system

• BLT is a key component for reducing transverse emittances and increase luminosity


f Basic BLT System

K * (A - B) /(A + B)

Beam

A

B

StriplinePickup Position

PhaseAmplitude

Tuneetc

Signal Processing

Analysis


f Striplines and Fanout

TeV Stripline Parameters:– ~ 30 dB directionality

– 1 meter long (< 1/4 )

– D = 83 mm

– 0.65 dB/mm Sensitivity

MI and Recycler Stripline Parameters:– Unidirectional

– 1.4 meter long (1/4 )

– D = 110 mm

– 0.50 dB/mm Sensitivity

~300 ns, 7/8" Heliax




Ver

tical

Hor

izon

tal

VerticalStripline

HorizontalStripline

Pro

tons

Upstream A

Downstream A

Downstream B

Upstream B

PassiveComponent

Fanout

Upstream A

Upstream B

Downstream A

Downstream B

Proton A+B

Proton A-B

Pbar A-B

Pbar A+B

Proton A

Proton B

Pbar A

Pbar B

Proton A+B

Proton A-B

Pbar A-B

Pbar A+B

Proton A

Proton B

Pbar A

Pbar B


f

Operational Systems


f Tevatron BLT

• For transfers from Main Injector to Tevatron• Requirements (in order of importance – V. Lebedev):

1. Measure initial injection oscillations for every proton and pbar bunch – first 50 turns with <50 m resolution

2. Measure tunes, coupling and chromaticities for every bunch– > ~1000 turns

3. Monitor beam position before quench– ~ last 500 turns saving beam waveforms

• Beam formats:– Pbar:

• Four 53 MHz bunches separated by 392 ns at 150 GeV

– Protons: • Single 53 MHz bunch at 150 GeV


f Tevatron Scope BLT

• In Operations• Use Tektronix TDS7104 as fast

waveform digitizer– 2.5 GSample/sec/channel– Segmented memory– Embedded Celeron PC

• Samples proton bunch or four pbar bunches per transfer

• Signal processing analysis on waveform in Scope PC

• Decimate data to single position per bunch– Pbars – 64 turns– Protons – 256 turns

GPIB

ACNET

Scope PC

Tektronix TDS7104

MUX

Horz A+B

Horz A-B

Vert A-B

Vert A+B

CH 1

CH 4

CH 3

CH 2

Horz A+B

Horz A-B

Vert A+B

Vert A-B

Horz A+B

Horz A-B

Vert A+B

Vert A-B

PROTONS

PBARS


f Tevatron Scope BLT Results

First Pbar Transfer Sixth Pbar Transfer

1 12 3 4 2 3 4

4 pbar bunches per transfer; 64 turns per bunch; closing on second bunch


f Tevatron Scope BLT

• Position calculation:X = K * (A – B) / (A + B)

Resolution: ~ 140 m

• Calculate oscillation phase and amplitude from first 16 turns

• Correct injection magnets for next transfer for amplitudes > 0.25 mm

Betatron phase and amplitude for all 36 pbar bunches


f Tevatron Scope BLT Status

• Tektronix scope system in operations– Limited by slow internal data transfer

• ~20 seconds for 64 turns for pbars

• Improvements– New scopes have increased memory – two scopes just arrived

• Allows for ~800 turns for pbars, ~2000 turns for protons

– Upgrade scope software to improve internal data transfer• Increase acquisition speed by ~ x10

– Modifying position algorithm to improve resolution• ~ 30 to 50 m

– Integrate improvements over next few weeks


f Main Injector BLT

Requirements:– Measure position for first 1024 turns for all pbar bunches at

injection from either Accumulator or Recycler• “Hot” pbars from Tevatron in future

Beam Formats:1. Accumulator to Main Injector – Four batches of 7 to 13 bunches

of 53 MHz at 8 GeV

2. Recycler to Main Injector – Four bunches at 2.5 MHz at 8 GeV

3. Tevatron to Main Injector – 36 single bunches at 53 MHz at 150 GeV (Hot pbars)


f Main Injector BLT in Operations

• Using older AM/PM modules (see J. Crisp talk on BPMs)– Originally designed for eighty-

four 53 MHz bunches– Lower efficiency for 7 bunches– Less resolution– Won’t work for 2.5 MHz

• Digitize at 53 MHz• LabView controls acquisition

and analysis• Output 1024 vertical and

horizontal positions plus fractional tunes and betatron phase and amplitude to ACNET

RF

Beam Sync

PC

Gate

Controller

UCD

AM/PMModule

A

B

Position

Intensity

AM/PMModule

A

B

Position

Intensity

Dig

LabViewACNET

Horz

Vert

VXI


f Main Injector BLT Results

•Phase and amplitude for 9 transfers•Correct for amplitude > 0.5 mm

•Positions and tunes for first 1024 turns•Correct on second bunch in transfer


f Main Injector BLT Status

• Present system based on old AM/PM modules– Adequate for closing but needs updated to more responsive system

• System can not measure 2.5 MHz beam from Recycler

Plan:

• Installing Digital Receiver system for 2.5 MHz beam– Installation occurring now

• Need to replace present 53 MHz system– Decision to be made on choice of Digital Receiver system or

Scope system


f Recycler BLT

ACNET

Horz

Vert

RFAmpA 5 MHz

LP

RFAmpB 5 MHz

LP

RFAmpA 5 MHz

LP

RFAmpB 5 MHz

LP

VME

Power

PC

RFTrigger

DR

DR = Digital Receiver

• Requirements:– Measure position for first 1024 turns

for all bunches at injection from Main Injector to Recycler

• Waveforms:– Four 2.5 MHz pbar bunches at 8 GeV

• System based on Digital Receiver technology– Uses Echotek digital receiver

• Just into Operations


f Digital Receiver Options

Fast ADC

Digital Mixer(down conversion)

Filters andDecimation

Amplitude and Phase

Single

Channel

A, B or A-B, A+B • Hardware Option (see J. Crisp talk on BPMs)– 8 channel EchoTek card (VME64)

– 65 MHz ADC, 14 bits

– Hardware digital mixer, filters and decimation

• Software Option– 8 channel Struck digitizer (VXI)

– 100 MHz ADC, 12 bits

– Software digital mixer

– Correlation algorithm to measure channel amplitude


f Recycler BLT

Positions and tunes for 1024 turns


f Recycler BLT Status

• System in operations for about one week

• Closing routinely to < 0.3 mm

• No changes planned to system


f

Systems in Development


f TeV Scope BLT Phase Detector

• Measures phase of four pbar bunches relative to RF using Tektronix 7104 scope

• Measurement point every 18 turns– 64 turns is really 1100

turns

• Phase error of ~11 degrees (~0.55 ns)– Resolution ~ 1 degree (50

ps)

1 2 3 4


f Tevatron Digital Receiver BLT

RF

Beam Sync

PC

Gate

Controller

UCD

A

B

A

B

Dig

LabViewACNET

Horz

Vert

VXI

30 MHz LPRF amp

30 MHz LPRF amp

30 MHz LPRF amp

30 MHz LPRF amp

Software version of Digital Receiver system for pbars

• 30 MHz LP to ring single 53 MHz bunch– Ring for ~100 ns

• Digitize at 100 MHz

• Correlate with normalized response function

• Generate position and bunch phase for >1024 turns


f TeV Digital Receiver BLT

Horizontal Tunes Vertical Tunes



Vertical Position vs Turn Horizontal Position vs Turn



Comparison of position data to theory (courtesy of V. Lebedev)

+ Horizontal Position, --- Difference from fit Position, --- Difference from fitSynchrotron factored out


f Tevatron Waveform Movie

Proton injection

Vertical Stripline into fast scope

• Red = A-B

• Blue = A+B

• 1 to 2000 turns by 20

• 0.5 ns sampling

• Negative Vertical Chromaticity

• Longitudinal dampers off


f Head-Tail Measurements(courtesy of P. Ivanov)

0 200 400 600 800 1000 1200 1400 1600 1800 20001

0.5

0

0.5

10.75

0.75

xj 10

A j 10

A j 10

1.964 1031 j

0 200 400 600 800 1000 1200 1400 1600 1800 20004

2

0

2

43.213

3.4

xj 10

A j 10

A j 10

1.964 1031 j

Developing of the head-tail instability with dipole longitudinal configuration

Developing of the head-tail instability with monopole longitudinal configuration


f Chromaticity Measurement by the Head-Tail Monitor (courtesy of P. Ivanov)

O s c i l l a t i o n o f d i p o l e m o m e n t a l o n g t h e l o n g i t u d i n a l b u n c h l e n g t h :

L

gt

teAtY

cos,

0 headtheat0

0

y B e t a t r o n a n g u l a r f r e q u e n c y s h i f t d u e t o c h r o m a t i c i t y

L i s t h e t o t a l b e t a t r o n p h a s e s h i f t f r o m h e a d t o t a i l

B e t a t r o n p h a s e a d v a n c e f o r o n e a n d t h r e e t u r n s :

MaxTdtn

MaxTdtn

T

T

333

1

30

3

0

100

0

0

0

1300

12

2 fT

yy

Hzfn 30

107.47,0028.0,5725.0sec,5.2

4.3y


f Summary

• Tevatron, Main Injector 53MHz and Recycler 2.5 MHz operational for injection closing

• Main Injector 2.5 MHz being installed

• Upgrades progressing for Tevatron and Main Injector 53 MHz systems

• Multi-systems need to be evaluated and decision made on priorities and how many systems to support– Advantages and disadvantages of each system

– Need to guard against over design


f Cast of Characters

Instrumentation:Jim Crisp, Brian Fellenz, Eugene Lorman, Warren Schappert

Pbar Source: Dave McGinnis

Tevatron: Petr Ivanov, Valeri Lebedev

Advise and Consent: Church, Pasquinelli, Pordes and others

…with apologies to anyone forgotten

Beam Line Tuners

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