Status of the luminosity monitor 20 Oct, 2004 John Byrd

LARP Mtg 19-21 Oct 2004 page 1

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Status of the luminosity monitor

20 Oct, 2004

John Byrd



PeopleLBNL

– John Byrd– Bill Turner– Peter Denes– Massimo Placidi– Nathan Speed– Alex Ratti– Jean-Francois Beche– Marco Monroy– Jim Greer

• University of Pavia– Franco Manfredi– Gianluca Traversi– Wainer Vandelli



LHC Luminosity MonitorThe challenge:• High radiation environment (100

MGy/year)• Bunch-by-bunch capability (25 nsec

separation) with 1% resolution.

The solution:

• Segmented, multi-gap, pressurized ArN2 gas ionization chamber constructed of rad hard materials

9 cm



Luminometer Beam TestsUse beam test facilities at the ALS to

provide MIPs for the detector to test

• position sensitivity

• time response and gain

• accuracy

• operating experience over long time periods

Booster-To-Storage Ring spur:

• 1.5 GeV e- at 1 Hz rate

• 30 psec pulse length

• intensity from 1 to 1e9 e- (1e3 typical)

• daily access and availability

Storage Ring spill:

• 1.5 GeV e- with variable spacing

• 30 psec pulse length

• intensity of a few e-

• weekly access



•“delta-function” e- beam (50 ps); 1.5 GeV; 1 Hz•Adjustable intensity (typically ran at 20 pp±50%)

BTS Tests



BTS Setup

1 Hz 1.5 GeV e-



BTS Waveforms



Position Sensitivity• Raster scan detector through

pencil beam

• Record 4 quadrants:

x=(left-right)/sum

y=(top-bottom)/sum

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

-50 -40 -30 -20 -10 0 10 20 30 40 50

Table Y position [mm]

y COG

x=-5x=-4x=-3x=-2x=-1x=1x=2x=3x=4x=5x=0

y independent of x

•Ionization chamber works as a true 4-quadrant detector•x and y are independent (no crosstalk)•Position resolution < 110 µm

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

-50 -40 -30 -20 -10 0 10 20 30 40 50

Table X position [mm]

x COG

y=-5y=-4y=-3y=-2y=-1y=1y=2y=3y=4y=5y=0

x independent of y



Gas Tests• Chamber uses Ar (100-x %) + N2

(x%)

• Design was based on Monte Carlo calculations of gas properties

• Drift velocity is key parameter (determines speed)

I0

= xGAP/vD

00

2

1)( IdttIQ ∫ ==

I0 = 2 Q0vDPNGAP

= 9.7 e–/MIP/mm x 231 MIP/h x xGAP x P x NGAP

= 0.72 nA x vD [µm/ns] x P [Atm] x NGAP

xGAP



Detector response timeMeasure pulse response for

varying pressure, gas mixture, and voltage. Derive drift velocity from fit using electronics response.

0

5

10

15

20

25

30

35

40

45

0 500 1000 1500 2000 2500 3000 3500

E/p [V/cm/Atm]

Drift Velocity [um/ns] Ar (96%) N

2 (4%)

3 AtmG4 AtmG5 AtmG6 AtmGSimulation

Data show agreement withsimulation

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

70.0E-9 90.0E-9 110.0E-9 130.0E-9 150.0E-9 170.0E-9

Time [s]

Amplitude [4% gas / 4 AtmG]

Transresistance Amp

Simulation (Transresistance Amp)

Standard Readout

Pulses a bit longer than expected due to additional capacitance of detector/cable but still suitable for 25 nsec operation.



Simulate LHC Pulse Rate in the ALS

ionization chamber

lost electron

removeable lead

scraper

electron bunches primary EM shower

vacuum chamber

Fill pattern adjustable with 2 nsec spacing into 328 buckets. Test up to 24 nsec spacing.



Fast Pulse Beam Test Results

Quadrant 3 - 4% Mixture - 2.5 atm - HV = 500V38MHz Pattern

Time (μ )s-0.2 0.0 0.2 0.4 0.6 0.8 1.0

( )Amplitude V

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Gap

Quadrant 3 - 4% Mixture - 2.5 atm - HV = 500V19 MHz Pattern

Time (μ )s

-0.2 0.0 0.2 0.4 0.6 0.8 1.0

( )Amplitude V

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Gap

52 nsec, 11 bunches

26 nsec, 22 bunches

Spilled ALS beam provides a test of LHC conditions.

Further studies to determine if pulses can be deconvolved to 1% accuracy.



Results from 12 June 2004

-0.29

-0.28

-0.27

-0.26

-0.25

-0.24

-0.23

-0.22

Signal (V)

500040003000200010000

Time (nsec)

164 nsec bunch spacing



Recent results 26 nsec spacing

-0.282

-0.280

-0.278

-0.276

-0.274

-0.272

Signal (V)

500040003000200010000

Time (nsec)

26 nsec bunch spacing



26 nsec bunches zoom

-0.282

-0.280

-0.278

-0.276

-0.274

-0.272

Signal (V)

120010008006004002000-200

Time (nsec)

26 nsec bunch spacing Need to deconvolve pulses using measured single pulse response. Use empty buckets as absolute reference.



50

40

30

20

10

0

-109.10µs9.089.069.049.029.00

Time (microsec)

100

80

60

40

20

0

-20

9.5µs9.49.39.29.19.0

Time (microsec)

50

40

30

20

10

0

-109.10µs9.089.069.049.029.00

Time (microsec)

50

40

30

20

10

0

-109.10µs9.089.069.049.029.00

Time (microsec)

ch3

ch1 ch2

ch4

broken

Single pulse response-data from 6 July 2004-single bunch pattern in the ring-3 channels show base width ~25-30 nsec-SNR unable to resolve long tails…pulse train needed to see effect-good agreement with bench tests of electronics



Pulse train response

empty buckets

26 nsec

100

80

60

40

20

0

-20

Signal (mV)

10.0µs9.89.69.49.2

Time (microsec)



Deconvolution of overlapping pulses0.4

0.3

0.2

0.1

0.0

-0.1

-0.2

-0.322020018016014012010080

ns

single pulse response

0.4

0.3

0.2

0.1

0.0

-0.1

-0.2

-0.3500400300200100

ns

0.6

0.4

0.2

0.0

6005004003002001000

ns

Test deconvolution process using electronics driven by pulser

Further work in progress:-peak accuracy vs. SNR-effect on channel nonlinearity



Deconvolution0.6

0.4

0.2

0.0

-0.2

-0.4

-0.6

3210

µs

1.200

1.195

1.190

1.185

1.180

1.175

1.170

806040200

Example: 100 pulse train with small amplitude sinusoidal modulation (accidentally applied to pulser!)



Possible installation in IP2 and 8

• Effort to define envelope for installation at “low” luminosity IPs for use in p-p operations

• No TANs-IC detectors require supports and must be moved for Pb-Pb operations.

sufficient space for IC Lumi



FY04 Results• FY04 budget $162k• Detailed study of lumi test in FNAL booster radiation test facility;

eventually aborted• Engineered, designed and built first TAN-compatible prototype

chamber• Development of beam test facility at ALS

– booster test stand for precision tests at 1 Hz– storage ring test stand for 38.5 MHz tests

• ready to begin engineering of production prototype– improved mechanical design

• fixed arcing problems– optimised front-end electronics

• preliminary work for installation in IP2+8



Plans for FY05• FY05 budget expected to be $395k • Mechanical

– Design and build final prototype– HV distribution redesign (current setup uses PCB)– Radiation hardness of HV distribution components (resistors and

caps)– radiation hardness of chamber materials

• Electrical– Finalize preamp and shaping design– Integrate electronics into a package which meets CERN requirements– Demonstrate operation with CERN 40 MHz DAQ

• Beam tests– repeat detailed measurements of chamber response vs. voltage,

pressure, etc. (with new ATLAS graduate student)– develop test for amplitude calibration of detector– integrate CERN DAQ into beam tests at ALS– investigate precision 40 MHz beam source

Status of the luminosity monitor 20 Oct, 2004 John Byrd

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