Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://zebu.uoregon.edu/~uochep/talks/talks05/torrence-1.pdf Äàòà èçìåíåíèÿ: Sat Jul 9 00:19:36 2005 Äàòà èíäåêñèðîâàíèÿ: Tue Oct 2 11:26:29 2012 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: m 43

Extraction Line Diagnostics

ILC-BDIR WG4 Interim Workshop Royal Holloway University of London

Eric Torrence University of Oregon

Eric Torrence

1/19

June 2005


Mea Culpa

Real Work · SLAC/BNL/UK/France 2 mRad consortium (Yuri) · Ken Moffeit (Woods, myself)

Outline · X-line instrumentation overview · 20 mRad instrumentation reminder · 2 mRad instrumentation design · Polarization issues · Spectrometry issues Instrumentation = Energy Spect. + Polarimetry Mistakes (of course) are mine
Eric Torrence 2/19 June 2005


Beam Instrumentation Introduction
0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 490 492 494 496 498 500 502 504 Root(s) (GeV)

( -, - ), ( +, + ), ... dL -----dE L

0

s Fundamental Goal Spin-dependent absolute collision energy spectrum Typical Components · · · · · Beam Energy Beam Energy Width Beam Polarization Absolute Luminosity Differential Luminosity Spectrum

All are intrinsically related in fundamental goal
Eric Torrence 3/19 June 2005


Instrumentation Goals

Goals often defined by what is considered "achievable" · s understood to 50-100 ppm - m H , m t , m Beam energy necessary but not sufficient · Polarization P 0.25 % - A
LR X

at high energy
+

Goal for polarimeter, could use better, 0.1% with P · Absolute luminosity ALCPG view: L 0.2 % ("easy") Tesla view: L 0.01 % ("very hard") LEP expt. 3.4 â10
­4

Theory 5.4 â10
qq

­4

Motivations given are Z and

Baseline goals for high energy, high luminosity running Use mixture of beam-based and physics-based observables Redundancy is key to precision
Eric Torrence 4/19 June 2005


Why Downstream?

Polarimetry · That's what was done at SLC · Diagnostic for IP spin depolarization · Easier spin vector alignment? · Main detector backgrounds?

Energy Spectrometry · WISRD-style complimentary to upstream BPM · Possible to monitor IP disruption · Potential to get info on lumi spectrum

General strategy for high accuracy measurements: redundancy and complementarity

Eric Torrence

5/19

June 2005


Downstream Instrumentation Constraints Designing an extraction line at High Energy and High Luminosity is difficult (impossible?) Instrumentation needs imply the following additional constraints Polarimetry · Spin vector parallel at Compton and main IP jitter tolerance - spin vector alignment · Secondary focus at point of high dispersion polarimeter chicane · Desire for favorable transfer function (R22) · Quiet location for detector at compton endpoint Spectrometry · Production of "signal" synchrotron radiation · Line of sight to SR detectors outside beam stayclear · Secondary focus at SR detector plane

Additional constraints must be satisfied with realistic magnets, apertures, beam losses, and backgrounds (still to be done!)
Eric Torrence 6/19 June 2005


20 mRad optics design

Yuri Nosochkov - June 1st

Energy Polarimeter

2nd Focus = 2 cm y

Eric Torrence

7/19

June 2005


20 mRad instrumentation layout Ken Moffeit - LCWS
10 meters 10 cm

10 cm (y)
Energy Chicane
BVX4 BVX6 z=70.49 m z=75.09 m BVX3 BVX5 z=68.19 m z=72.79 m BVX8 z=83.59 m BVX7 z=81.29 m

BVX9 z=100.59 m

BVY1 z=120.59 m

Polarimeter Chicane
25 GeV

Synchrotron Stripe Detector z=143.69 m

BVY2 z=132.59 m 3 mrad energy stripe

SR Detectors
BVY3 z=152.59 m QFX4 z=156.59 m

BVX1 z=59.69 m BVX2 z=61.99 m

Stayclear
0 .75 m ra d

2 mrad energy stripe 45.59 GeV

Stripe Detector

Synchrotron

Compton IP

250 GeV

BPM

BPM

25.1 GeV

35.7 GeV

12.0 cm

0. 75 mr ad
2 mrad energy stripe 3 mrad energy stripe

1 7. 8 cm

z=64.29 m

Low Field BLEX

z=66.89 m

BLEX

BLEX BLEX z=77.39 m z=79.99 m WEX1 z=78.69 m

WEX1 z=65.59 m Wiggler

SR Fan

Wigglers
K Moffeit 4 Apr 05

Synchrotron Stripe Detector

Shielding

Cerenkov Detector

Key Points/Issues

C Detector

· Apertures: 20 cm gap for "wigglers", 20x40 cm for Pol Chicane dipoles Energy bandwidth, SR line-of-sight, stayclear, Compton endpoint · SR detectors slightly downstream of 2nd focus - resolution issue · Detectors very tight to nominal stayclear - background issue

Eric Torrence

8/19

June 2005


2 mRad optics design Yuri Nosochkov

Three vertical chicanes! Energy collimation at ~10% Enom Parallel beam at compton IP
Eric Torrence 9/19 June 2005


2 mRad optics design Yuri Nosochkov

Turtle Tracking X CIP

Turtle Tracking Y CIP

Eric Torrence

10/19

June 2005


2 mRad instrumentation layout
Polarimeter Chicane Energy Chicane
BHEX3A z=190.06 m x=-- cm BHEX3B z=192.36 m x=-- cm BYCHIC z=~198 m x=-- cm BYCHICM z~208 m x=-- cm

Ken Moffeit - June
2 mrad extraction line Plan View
10 cm 10 m
BHEX2 z=129.060 m x=71.25 cm SEXF2 z=116.66 m x=63.98 cm QEXF5 z=123.060 m x=67.73 cm

Focus z~214 m
2rd

BYCHICM z~218 m x=----- cm

BYCHIC z~228 m x=----- cm

BHEX3C z=194.66 m x=-- cm

Stripe Detector
Beam Stay Clear +- 10 cm

Synchrotron

Angle 10.563 mrad

20 x 50 cm
BYCHIE z~ 131.0 m x= cm BYCHIE z~151.0 m x= cm BYCHIE z=154.4 m x=----- cm

BYCHIC z=174.4 m x=----- cm Angle 3.621 mrad Angle 5.242 mrad

Angle 2.0 mrad

Angle 8.850 mrad Angle 7.138 mrad Angle 5.425 mrad Angle 3.712 mrad

Compton IP

BHEX4C z=m x= cm

BYCHIC z=106.46 m x=58.00 cm

QEXF4 z=112.460 m x=61.52 cm

QEXF4B z=118.860 m x=65.27 cm

Angle 6.863 mrad

SR Detectors

BHEX4B z= m x= cm BHEX4A z=~232 m x= cm

BHEX4D z= m x= cm BHEX4E z= m x= cm

BYCHICM z=82.360 m x=43.87 cm BYCHIC z=60.364 m x=30.973 cm

BYCHICM z=84.460 m x=45.10 cm

SEXF1 z=28.861 m x=12.51 cm QEXF1 z=26.161 m x=10.92 cm QEXF1B z=31.061 m x=13.79 cm Beam Stay Clear +- 10 cm

Angle 5.863 mrad

20 cm
Photon Beamstrahlung Cone +- 1 mrad

1 mRad Cone Wigglers
8 meters

Angle 2.0 mrad at IR

Y

Sextupole Quad Quad Quad

Stripe Detector

Synchrotron

2nd Focus 214 meters
Cerenkov Detector
17.8 cm 35 GeV
1 .3 2 cm

10 cm 5 cm 0 -5 cm -10 cm Dispersion = 66 cm 250 GeV

Beam Stay Clear 10cm

Side View

Compton IP
Angle -3 mrad Angle 3 mrad Angle 2 mrad

25.1 GeV

Angle -3 mrad

Angle 3 mrad

Dispersion = 20 mm 250 GeV

C Detector
Vacuum Chamber

Beam Stay Clear 10cm

Dispersion = 66mm 250 GeV

25 GeV

Wiggler Low Field
25 GeV

Energy Slit
Eric Torrence

3 mRad
25 GeV

2 mRad SR Detectors

Stripe Detector

Synchrotron

K Moffeit 20 Apr 05

11/19

June 2005


IP-Polarimeter differences
P(%)
3 2 1 0 3 2 1 0 0 5 10 15 dy / 0 5
NLC 1TeV

Depolarization in collision · Sokolov-Ternov and BMT precession · Overall lumi-weighted ~ 1/4 total depol. · P lum ~ 0.5%, should be re-evaluated with modern machine parameters IP-polarimeter spin precession (g ­ 2) = ---------------- 2
0

Outgoing Bunch

10

15

Lumi Weighted S-T BMT Total

· 1000x amplification, need spin vector longitudinal and parallel to ~ 50 µRad · Harder with 2 IPs (double spin rotators) · Must worry about solenoid in x-angle

y

New IP simulation (GuineaPig) with spin transport may help guide arguments here Ultimately want to measure these effects

Eric Torrence

12/19

June 2005


R22 IP Energy Polarimeter

|x chicane = R |x IP where x = { x, x', y, y', E / E } R22 most important as horizontal angles dominate
Spin Direction Spin Direction

Beam Direction

50 mrad

D e p o l a r i z a ti o n

at Compton IP (using R22)

D e p o l a r i z a ti o n

After IP

after IP

With 1% energy cut Luminosity-wted

Luminosity-weighted Horiz offset (x)

R22 = -0.6
13/19

Horiz offset (x)

Eric Torrence

June 2005


Negative vs. Positive Ken Moffeit - LCWS
50 mrad D e p o l a r i z a ti o n R22 = -0.595 after IP D e p o l a r i z a ti o n Spin Direction Beam Direction R22 = + 0.595 after IP

at Compton IP, using R22 With 1% energy cut Luminosity-wted Horiz offset (x)

With 1% energy cut Horiz offset (x)

(Moffeit, MÆnig, Woods, Schuler, Nososchkov) My understanding is that positive R22 possible, at expense of longer 2 mRad extraction line Only BMT, S-T (spin flip) evolution not included (need GP/Cain)
Eric Torrence 14/19 June 2005


Wiggler Design · Focus at detector plane WISRD-style · Wigglers reduce SyncRad alignment systematics Detector · Wigglers can be turned Plane off for bgd studies · Up/down to maximize y / l (resolution) IP Wigglers cm Split Option Detectors +20 0
1mRad

cm Joined Option Detectors +20 0
1mRad

-20 Large wiggler

-20 Small + Soft Bends

Eric Torrence

15/19

June 2005


Assorted Wiggler Issues Aperture constraints



d



min

2d?

Large 20 cm aperture unsuitable for "traditional" wigglers Dipole SR background Ebeam 50 250 500 Ecrit (MeV) 0.3 34 275 (for 1 mRad/m) E
crit

= 3 hc 3 / ( 2 )

Need Wigglers at all? I Endpoint of dipole SR x Too sensitive to width?
Eric Torrence

I

Sum of both

dI ----dx

x Subtract wiggler-off background?
16/19 June 2005


2 mRad detector plane

Horizontal bend to align IP - CIP spin vectors

Separates SR and Compton signal

SR Stripe

Compton Electrons

Looks very nice

Outgoing Beam

Eric Torrence

17/19

June 2005


2 mRad detector plane

Dipole SR is potentially a serious background problem for both detectors...

Gas Cerenkov: 10 MeV Quartz Fiber: 0.7 MeV

High Flux of HE SR Will strike surrounding material (30-300 MeV) H Bend Pol Chicane

Need careful study of backgrounds and shielding options

Not at all clear whether this will work! (2 mRad or 20 mRad) Energy Chicane

Eric Torrence

18/19

June 2005


Summary and Plans Summary · 2 mRad vertical crossing-angle w/ diagnostic chicanes available for Ebeam = 250 GeV · Not obviously worse than 20 mRad solution · No detailed study showing any of this will work! Immediate Plans · I have so far failed to get BDSIM running for X-line studies, but Orsay group (Olivier Dadoun) have this working now (IP->dump) · Have 2 mRad and 20 mRad model available for spectrometer (and eventually polarimeter) performance and background studies by Snowmass · Start some real thought on wiggler design/usage Longer Term · Incorporate realistic solenoid, DID, anti-solenoid, final doublet fringing field, etc · Detailed Geant4 detector description
Eric Torrence 19/19 June 2005