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Energy Spectrometer Designs and Beam Tests

July 29th, 2004 Victoria Linear Collider Workshop Victoria, BC

Eric Torrence University of Oregon

З З З З

Spectrometer Goals Post-IP observables Wisrd-style design and testbeams BPM-style design and testbeams

Eric Torrence

1/15

July 2004


Energy Measurements

0.05 0.04 0.03 0.02 0.01 0

490

492

494

496

498

500

s
+e+e- Еe+e- e e Е
Eric Torrence

502 504 Root(s) (GeV)

e+e- Е ЕЕ
2/15

1 2

1

2 e+e- Еe+eJuly 2004


Spectrometer Dilemma

0.06 0.1 0.08 0.06 0.04 0.02 0

In

0.05 0.04 0.03 0.02

Out

+ - E b + E b s
240 245 255 Ebeam (GeV) 250

0.01 0 240 245 255 Ebeam (GeV) 250

0.05 0.04 0.03 0.02 0.01 0

490

492

494

496

498

500

502 504 Root(s) (GeV)

What can a beam energy measurement really tell you?
Eric Torrence 3/15 July 2004


What really matters?
Expected Events
mW = 80.330 GeV W = 2.093 GeV

Breit Wigner Reconstructed

Variance and uncertainty of bias, not the bias itself is the problem! s - s' from ISR is large...

Beam-beam interactions are not predictable like ISR

60

70

80 90 100 qql Invariant Mass (GeV)

in s - 2 E b vs. Vertical Offset (truncated range)
Ecm (MeV) Ecm (MeV)

NLC 500
-800

TESLA 500
-1000 -1200

-1000

-1200 -2 -1 0 1 2 Offset (nm)

-1400 -2 -1 0 1 2 Offset (nm)

Need to measure this to understand to < 50 MeV
Eric Torrence 4/15 July 2004


Extraction Line Energy Study Guinea Pig Inputs З Input NLC and TESLA TRC files З Vary vertical offset by Б 3 nm 30 GP runs per machine Some estimate of `realistic' variations Guinea Pig Outputs З lumi.ee.dat - Lumi weighted s spectrum З beam.dat - Disrupted beam files s is what we care about Disrupted beam is what we can measure Analysis
+ - Fit E b and E b (best a spectrometer could do)

Correlate s to fit parameters in truncated range +/- 10 GeV of peak Precondition for full spectrometer simulation (grad student working full time for Summer)
Eric Torrence 5/15 July 2004


NLC Fit Example
Events / ( 0.075 ) 300 250 200 150 100 50 0 240 Events / ( 0.075 ) 242 244 246 248 250 252 254 Beam Energy (GeV)

250 200 150 100 50 0 240 242 244 246 248 250 252 254 Beam Energy (GeV)

Circe Gaussian P ( E ) = g ( E ;E 0, ) + a where x = E / E'

0



E

x a 1 ( 1 - x ) a 2 g ( E ' ) dE '

Plus an extra Gaussian (NLC only) Total of 8 parameters (5 for Tesla) Implemented in RooFit, easy to make complicated observables
Eric Torrence 6/15 July 2004


Correlation Examples
NLC 500
Ecm (GeV)

TESLA 500
-2.3 -2.4 -2.5 -2.6 -2.7 -2.8 -2.9 -3 -3.1 -3.2

-2.3 -2.4 -2.5 -2.6 -2.7 -2.8 -2.9 -3 -3.1 -3.2 -4.2 -4 -3.8 -3.6 -3.4

s vs. E

+ b

+ E

- b

Modest (negative!) correlation seen with cold Adequate if no beam-beam correlations?
Ecm (GeV)

-4.2

-4

-3.8 -3.6 -3.4 + (GeV)

-2.4 -2.6 -2.8 -3 -3.2 0.8 0.85 0.9 0.95 1 a0

-2.4 -2.6 -2.8 -3 -3.2 0.6 0.65 0.7 0.75 0.8 a0

s vs. Circe Parameters

-2.4 -2.6

-2.4 -2.6 -2.8 -3 -3.2 3 4 5 6 7 8 a1 9 9.5 10 10.5 11 a1

Nothing jumps out Work beginning on better observables (like tail fraction)

-2.8 -3 -3.2

-2.4 -2.6 -2.8 -3 -3.2 -1 -0.8 -0.6 -0.4 -0.2 0 a2

-2.4 -2.6 -2.8 -3 -3.2 -0.6 -0.55 -0.5 -0.45 -0.4 a2

Eric Torrence

7/15

July 2004


Next Steps Extraction Line Design
Vertical Disp. (mm) 600 400 200 0 -200 -400 -600
20% Enom 1 mRad Stayclear 3 mRad Dipoles SR Fan Detector Plane To Dump 250 GeV Beam Horiz. Wigglers Compton Endpoint 750 MeV/mm

0

20

40

60

80

100

120 140 Longitudinal (m)

Propagate output beams to detector plane Detector Plane Concepts cm Split Option Detectors +20 0
1mRad

cm Joined Option Detectors +20 0
1mRad

-20 Large wiggler
Eric Torrence 8/15

-20 Soft Bends
July 2004


Detector R&D Quartz fiber SR prototype З З З З З Intrinsically fast E > 200 keV threshold Lower crosstalk multi-anode PMT readout Easy gain adjust

Prototype Geometry 8 x 100 Еm fibers (Left) 8 x 600 Еm fibers (Right) 1 mm pitch Multi-anode PMT Up to 64 ch. readout Single HV input High gain Other Detector Possibilities Wisrd-style wires Diamond/silicon strips Visible or UV imaging (CCD) Pinhole-style imaging ...
Eric Torrence 9/15 July 2004


ESA Beam Tests

Exclude

BPM tests

SR tests Use original spear wiggler E c = 0.9 MeV at 28 GeV eE c = 0.1 - 0.2 MeV from bends Rough Guess: 3 з10 PE/pulse S/N ~ 100 - 1000 (TN-2004-7: Ray Arnold) Detailed simulation starting Compare various detectors Quartz fiber array Wisrd wire array Visible CCD (diagnostic)
6

Eric Torrence

10/15

July 2004


BPM-based Spectrometer
0.9mm

180Еrad 10m 10m

Design Parameters Limit energy growth 360 ЕRad -> 0.5% Extra space for in/out triplets Need 50-100 nm BPM resolution, stability, accuracy Tiny energy variation to IP

beta distribution may not be ideal

Eric Torrence

11/15

July 2004


BPM R&D

DESY З 5.5 GHz BPM prototype З Testing (now?) at ELBE linac (Dresden) З ~ 16 ns expected З 2 mV/100 nm estimated

ATF - NanoBPM З Multibunch tests З sub-100nm observed Installed LLNL super-girder, fancy interferometer...
Eric Torrence 12/15 July 2004


ESA Tests

Test mechanical and electrical stability, particularly in "hostile environment" Explore sources of long-term drifts from 50 nm stability Test time resolution of RF BPMs Moveable stage tests response characteristics of BPMs
Eric Torrence 13/15 July 2004


ESA spectrometer tests

Synchrotron detector test З Verify simulation for quartz fiber response, S/N З Demonstrate resolution З Check "operational robustness" Oregon, SLAC, ??? RF BPM test З Mechanical and electrical stability З RF response to "realistic beams" З Time resolution Notre Dame, Berkeley, UC London, Cambridge, SLAC

Timescale: Summer 2005 First steps towards ultimate goal: Full scale spectrometer prototype Timescale: Summer 2007?

Eric Torrence

14/15

July 2004


Final Thoughts Want to be able to reconstruct at least s independently with spectrometers and physics-based measurements. More work needed to show viability of downstream spectrometer to provide interesting information Need more work on physics-based determinations Neither spectrometer is a simple engineering exercise Testbeam program in End Station A evolving to demonstrate hardware feasibility

Useful to reconsider some wacky ideas from the past?
Silicon Microstrip Detector (SMD) Hydrogen Gas Jet (GJT) Scattered electron LEP beam Electromagnetic Calorimeter (ECAL) E1 1 2

Recoil Proton Tracker

L
15/15

E2
July 2004

Eric Torrence