Storage Ring EDM Technical Review – 12/7/2009 Edward J. Stephenson, IUCF0 Polarimeter Development...

Storage Ring EDMTechnical Review – 12/7/2009

Edward J. Stephenson, IUCF 0

Polarimeter Development

Hello

STORAGE RINGPOLARIMETRY




Requirements

1. Measure a change in the vertical polarization with a sensitivity of 10−6. Provide a continuous record with time. Reduce systematic errors to below the sensitivity limit.

2. Track the magnitude of the polarization with time.

3. Provide transverse (X) asymmetry data continuously for control. Operate at high efficiency.




Requirements

1. Measure a change in the vertical polarization with a sensitivity of 10−6. Provide a continuous record with time. Reduce systematic errors to below the sensitivity limit.

2. Track the magnitude of the polarization with time.

3. Provide transverse (X) asymmetry data continuously for control. Operate at high efficiency.

Development proposal made to COSY-Jülich in 2007.Ring design was for 1 GeV/c deuteron beam (250 MeV)

Best scheme requires deuteron scattering from carbon.

Conduct study using as much existing equipment as possible.

(Begin studies of production/preservation of horizontal polarization.)

Deuteron and proton polarimeters are similar.




Analyzing Reaction Characteristics

d+C elastic, 270 MeV

available at COSY

desired range

FOM = σA2

Y.

Sa

tou

, P

L B

54

9,

30

7 (

20

02

)






available at COSY

desired range

FOM = σA2

inelastic scattering

(d,p) reactions + breakup

Inelastic and(d,p) reactions

follow trendof elastic. Sokeep them!

Y.

Sa

tou

, P

L B

54

9,

30

7 (

20

02

)






available at COSY

desired range

FOM = σA2

inelastic scattering

(d,p) reactions + breakup

Inelastic and(d,p) reactions

follow trendof elastic. Sokeep them!

DAQ does not keep just single channel.Include low Q-value reactions.

(Tensorcan be

large anduseful.)

Y.

Sa

tou

, P

L B

54

9,

30

7 (

20

02

)




Polarimeter Properties

Broad acceptance for high efficiency:

Angle range = 5° to ~20°Excitation range < ~40 MeVNo particle identificationStable properties rely on stable gains, thresholds, etc.Build and calibrate (including systematic errors properties)

Implications for polarimeter design:

Low analyzing power particles can be removed with an absorberCount everything above thresholdDAQ can be simple (scaler) and fast for high statistics, low dead timeDetector must be insensitive to rate changesThick targets are required (several cm) for high efficiency (~1%)

Design features that go beyond current polarimeters:

Extraction from a storage ring onto a thick internal targetReduction of systematic error effects to 10−6




COSY ring:

Use EDDAdetector

COSY tests

EDDA detector:

Rings and bars to determine angles.

Tube target,extracts alonginside edge.




COSY ring:

Use EDDAdetector

COSY tests

EDDA detector:


FRONT: This iswhere EDDA lookslike an EDM polarimeter.

REAR: This is acheck of methods

Run at 0.97 GeV/c.




COSY ring:

Use EDDAdetector

COSY tests

EDDA detector:


LEFT

UP

DOWN RIGHT

Azimuthal angles yield two asymmetries:

RL

RLEDM

UD

UDg

2




Target Concept

Target solution found at COSY:

15 mm

White noiseapplied to

electric fieldplates.

beam core

expanded vertical phase space

endview

maximumallowed at

COSY

Do enough particles penetrate far enough into the frontface to travel most of the way through the target?

This requires a comparison of the efficiency with model values.




Rocker test:

Target Vertical Angle and Efficiency Test

How sensitive to vertical angle?

+

−

Best alignment with target front edge.

FRONT

BACK

× 10−3

Efficiency is the sum ofevents into the down andup segments of thedetector divided by theparticles lost from the beam.

Measurements arehigher than Monte Carlo predictions basedon model of EDDAdetector and deuteron-carbon reactions,including elastic,inelastic and transfer.




Rocker test:



+

−


FRONT

BACK


Slope corresponds totypical depth in targetof 0.2 mm, larger thanthe multiple scatteringwidth of σ = 0.013 mmafter 15 mm of carbon.

depth


× 10−3




Rocker test:



+

−


FRONT

BACK


Slope corresponds totypical depth in targetof 0.2 mm, larger thanthe multiple scatteringwidth of σ = 0.013 mmafter 15 mm of carbon.

depth


× 10−3

Efficiencies are low (×10) because ofthinner target and larger minimum angle.

Success.




Systematic Error Effects

Goal: keep errors in change of asymmetry to less than 10−6.

Things can change:geometryrate

Use standard tricks

↑ + ↓ L + R )()(

)()(

1

1 2

RL

RLr

r

rpA

(good to first order in the errors)

Correct effects arising at higher order

Try to use detector information: correction parameters

Geometry:)()(

)()(

1

1 2

RR

LLs

s

s

Rate: RL (instantaneous rate)

This requires a calibration of sensitivity to systematic errors.

Will this work?




Tests made at the KVI (2007)

130 MeVpolarized deuterons

18°

carbonribbontarget

Phoswichscintillationdetectors

The cross ratio fails at second order in the errors.

222

22

2223

2 )1(11

21

1(exp) x

x

A

x

A

Aux

x

A

Au

u = p(+) – p(−), p(−) < 0

Calculation based ondeuteron elasticscattering data at130 MeV and measuredbeam polarizations.

“true” asymmetry

observed asymmetry

Measure effects using errors >100 bigger than expected.

(Note: Asymmetry will also be larger.)




COSY results

Scan: position −2 to 2 mm angle −5 to 5 mradRate varies during store

Make a linear fit tothe data from thestores. Assume thezero rate point isindependent of rateand can be usedfor the analysis ofgeometry effects.

Use the slope forthe study of rateeffects (pileup).

1 Rate and geometry effects are separable.




COSY results

2

X points

Angle points

10%

Corrections for X and θ match.One index can be used for both.

0.1%

For the cross ratio, second ordereffects are smaller.

Analyzing power Ay = 0.35 (front).

Correction Parameter

Correction Parameter




COSY results

Tests were made with the beam shifting by 4 mm during the store.

uncorrected

corrected forrate and geometry

V+ polarization case

slope: −1.4 ± 28 × 10−6 /s




COSY results

Tests were made with highrate and displaced beam.

uncorrected


T− polarization,2 mm displaced

slope: −4 ± 11 × 10−6 /s

corrected for rate




COSY results

3

Tests were made with highrate and displaced beam.

uncorrected


T− polarization,2 mm displaced

slope: −4 ± 11 × 10−6 /s

Corrections work.

For deuteron EDM ring: position changes < 10 μm initial vertical ε < 0.01gives control of systematicsto < 30 ppb, well underrequirement.

Scaling down:

cross ratio:A’/A = 0.0055ε = 0.01Δp = 0.05use (A’/A)ε2Δp

Since asymmetry depends only on count rates andcalibration coefficients, we get results in real time.

corrected for rate




μ-solenoid test

add 60-turn solenoidto ring running 100A

EDDA

polarity knownonly to COSY




μ-solenoid test

add 60-turn solenoidto ring running 100A

EDDA

polarity knownonly to COSY

data sample from rear detector

Solenoid: ON OFF

Data correction forrate brings averageonto straight line.

data excludedwhile magnet ramps

Prediction: 0.87 mradMeasured: 1.4 ± 0.4 mrad

Polarityagrees!




Protons

Near 230 MeVthe forwardcross sectionand analyzingpower arefavorable.

proton + carbon elastic scattering

We can expect:efficiency ~ 1.1 % (over 2π)analyzing power ~ 0.6

with some selection on elastics

HO Meyer, PRC 27, 459 (1983)




Polarimeter

Location of polarimeter in (half of) storage ring straight section

beam

Polarimeter:Note that thedetectors forthe counter-rotating beamshare the targetat the center ofthe quadrupole.

Injection system

RF solenoid used to precesspolarization of opposite bunchesinto the ring plane.




Polarimeter

(Half) Polarimeter in the ring:

cm

One target isshown. Wewant a targetavailable fromat least theleft, right, upand downdirections.

Quadrupoles hereare larger aperturefor clearance.

5° to 20°acceptance

Generic detector: (?) Multi-resistive plate chamber (?) Micro-megas (?) Gas electron multiplier (?) …other

Absorber to removelow analyzing powerparticles. (Detectorchoice can also givediscrimination.)

Equal rate readout pads

Rate = 800 /s/pad

In one store: 4105.1




Polarimeter


cm







Rate = 800 /s/pad


MRPC prototypeMRPC prototype

GrazianoGraziano

MRPCFrascati, U. Rome




Polarimeter


cm







Rate = 800 /s/pad


Micro-MegasINP Demokritos, Saclay, BNL




R & D 3-year Plan

Year 1: Simulation and design of proton polarimeterDatabase creation (cross section and analyzing power)Monte Carlo simulationEngineering design (including electronics)

Detector selectionPrototype tests (COSY, KVI, IUCF…)Inclusion in Monte Carlo simulation

Year 2: ConstructionParts procurement, machine shop, assembly

Installation (at COSY)

Year 3: Commissioning and calibrationDesign verificationOperating point determinationMeasurement of systematic error sensitivity

Goals (milestones) Produce a working EDM polarimeter for the ring




Resources needed:

R & D 3-year Plan

Note: This is an opportunity for separate funding throughIndiana University or other EDM Storage Ring institutions.

Costs (k$) withIU overhead

Personnel post-doc 300student 140

Travel 140

Construction design 60fabrication 160

Other (add ~1/4) 200

TOTAL 1,000




Polarimeter Development Team: (participating at COSY)

Indiana: Ed Stephenson*, Astrid Imig (BNL)

KVI-Groningen: Gerco Onderwater*, Marlène da Silva e Silva, Klaas Brantjes, Duurt van der Hoek, Wilburt Kruithoff, Oscar Versolato

COSY Jülich: Ralf Gebel, Andreas Lehrach, Bernd Lorentz, Dieter Prasuhn, Hans Stockhorst

BNL: Vasily Dzordzhadze, Don Lazarus, Bill Morse, Yannis Semertzidis

Frascati: Paolo Levi Sandri, Graziano Venanzoni

U. of Rome: Francesco Gonnella, Roberto Messi, Dario Moricciani

Thanks to: Olaf Felden (COSY), Frank Hinterberger (Bonn), Rudolf Maier (COSY), Hans Ströher (COSY), Univ. Münster

Regis U.: Fred Gray

* Spokespersons for polarimeter development

EDM Polarimeter Team

Storage Ring EDM Technical Review – 12/7/2009 Edward J. Stephenson, IUCF0 Polarimeter Development...

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Transcript of Storage Ring EDM Technical Review – 12/7/2009 Edward J. Stephenson, IUCF0 Polarimeter Development...