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Beam Instrumentation Activities in US
ECFA/DESY Linear Collider Workshop April 1st, 2003 NIKHEF, Amsterdam

Eric Torrence University of Oregon with M. Woods and D. Cinabro З "Status Report" document З High priority items З dL/dE studies
http://www.slac.stanford.edu/~torrence/ipbi/
Eric Torrence 1/12 April 2003


Polarization Proposal

Polarization Needs З Target P / P = 0.25% per beam SM, SUSY, other asymmetries З Recognize desire for P
eff

/P

eff

= 0.1%

Positron Polarization

Strawman Polarization Proposal З Compton polarimeter at post-IP chicane

З 2% pulse stealing for undisrupted beams

З WW (t-channel) asymmetry Forward tracking...

Eric Torrence

2/12

April 2003


Energy Proposal Energy Needs З Need 200 ppm from 2 m t < s < 1 TeV m t , m H ~ 50 MeV З Recognize desire for 50 ppm at 2 m Are we missing something?
W

...

Strawman Energy Proposal З BPM-style at upstream 1mRad bend RF BPMs З WISRD-style at post-IP chicane Energy width? З Forward tracking 200-500 mRad ( ЕЕ ) Also, machine diagnostics for width ...

Eric Torrence

3/12

April 2003


Luminosity Proposal* *More Speculative Luminosity Needs З Target dL / dE precision at 1% (tails) 0.1% (core width), 200ppm on mean s' З Target relative L precision at 0.01% Threshold Scans, Z calibration З Target absolute L / L ~ (0.3 - 0.5)% Hadronic cross-section Contact interactions Need Input from Physics Groups Strawman Luminosity Proposal З З З З З Forward Bhabha calorimeter Forward tracking 200-500 mRad Pair monitor Beamstrahlung diagnostic monitor Radiative Bhabha monitor downstream Also, other machine diagnostics for instantaneous luminosity
Eric Torrence 4/12 April 2003


Highest Priority dL/dE analysis З Analysis to extract both tail and core З Understand external inputs (beam energies, widths, offsets, etc...) З Understand beamstrahlung correlations (dispersion, head-tail, disruption angle) З Possible to extract physics correlations (Beam energy, polarization, total lumi) Extraction line studies З Polarimeter/Spectrometer possible? З Backgrounds? З Detailed design... Forward tracking З Need realistic conceptual design З Understand systematic limits (alignment) З Understand machine/physics backgrounds Energy width З How well can this be measured in real time З Understand expected beam instrumentation З Extraction line WISRD spectrometer?
Eric Torrence 5/12 April 2003


Bhabha acolinearity
1 350 GeV Machine + ISR + Beamstrahlung + 0.3% Linac

10

-1

Pandora Gaussian energy spread Core

10

-2

Tail
10
-3

10

-4

300

310

320

330

340

350

360

Collision Energy (GeV)

Highly dynamic distribution... Linac energy spread dn / dE


E
Eric Torrence 6/12 April 2003


Acolinearity Problems Acolinearity measures boost, not s Beamstralung Correlations З Disruption effects З Early-late correlations

Higher L, less tail

Lower L, more tail

Probably can't trust simulation alone... Final State Beamstralung Interactions e f

e BS ISR FSR BS

f

Particularly important for LA Bhabhas?
Eric Torrence 7/12 April 2003


Energy Spread Studies Use TRC simulated `imperfect' machine Feed to GuineaPig for IP simulation No Beamstrahlung for now!!! (M. Woods using A. Seyri) Energy vs Z s'

NLC 500 Б 0.4 % range indicated! Mean collision energy offsets NLC File L
(1034 cm-2 s-1) (ppm)

1 2.0
+547

2 2.0
+365

3 1.8
+512

4 2.0
+244

5 1.7
+647

6 1.7
+707

< s' >

+450 ppm lumi-weighted mean offset ~180 ppm variance... (Energy correlation + head-tail lumi correlation)
Eric Torrence 8/12 April 2003


Tesla Results Use TRC simulated `imperfect' Tesla machine No Beamstrahlung for now!!! e+ Energy vs Z s'

Tesla 500 Б 0.15 % range indicated Mean collision energy offsets Tesla File 1 2 3.2
+71

3 3.3
+8

4 3.6
+35

5 3.2
+72

6 3.3
+36

L (1034 cm-2 s-1) 3.3 (ppm) +95

+50 ppm lumi-weighted mean offset ~30 ppm variance...

Beamstrahlung will only make this worse...
Eric Torrence 9/12 April 2003


Energy Correlations

ECM

NLC

Б 2 GeV

Tesla

GP Interaction Time
Eric Torrence 10/12 April 2003


Other Concerns Energy Correlations З not measured by acolinearity З need beam energy profile as input З correlates with dL/dE, polarization NLC profile may be `fixable'... Disruption Angles 50 ЕRad Tesla

Large compared to accuraccy 50 ЕRad Sensitive to beam offsets/jitter...
Eric Torrence 11/12 April 2003


Test Beams Need Specific Requests З З З З Energy Spectrometer Polarimetry Forward Detectors dL/dE???

Current and Proposed SLAC Programs З E158 (running) Polarized source, RF BPMs, Pol asymmetries З Deep Ineleastic Scattering (proposal soon) Precision polarimetry (0.25%) З LYNX (proposal not soon?) FF dynamics, polarimetry, spectrometers, gamma-gamma, etc...

Need a more specific list of R&D items to be addressed with specific test beams...

Eric Torrence

12/12

April 2003