MOLLER Spectrometer Update

MOLLER Spectrometer Update

Juliette M. Mammei

MOLLER Collaboration Meeting May 8,9 2014

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Future Priorities (from last meeting)

• Physicist input to engineering (highest priority)o Magnetic force studieso Sensitivity studieso Design of the water-cooling and electrical serviceso Radiation doses (brought up by companies)

• Optimization of the opticso He bag/central beam pipeo Multiple magnetso No negative bendo Iron in coils

• Engineering work (MIT/Bates)o Design of support structureo Vacuum vessel design

Lower priority


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• Forces with asymmetric coils

– http://ace.phys.virginia.edu/MollerSpectrometer/297 (Jason)– http://ace.phys.virginia.edu/MollerSpectrometer/298 (Juliette)– http://ace.phys.virginia.edu/MollerSpectrometer/299 (Juliette)– http://ace.phys.virginia.edu/MollerSpectrometer/300 (Juliette)

• Radiation dose on coils

– http://ace.phys.virginia.edu/MollerSpectrometer/305 (Tyler)– http://ace.phys.virginia.edu/MollerSpectrometer/306 (Seamus)

• Coil sensitivities

– http://ace.phys.virginia.edu/MollerSpectrometer/287 (Sakib, Juliette preliminary)– http://ace.phys.virginia.edu/MollerSpectrometer/308 (Tyler)– See slides

• Support Structure– See slides

• Vacuum vessel– See slides

Bids

http://ace.phys.virginia.edu/MollerSpectrometer/297


















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Forces

NewOld

Coil offForces on coil to beam left with adjacent coil off


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Forces

Old

New

Coil

off


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Sensitivity Studies• Need to consider the effects of

asymmetric coils, misalignments etc. on acceptance

• This could affect our manufacturing tolerances and support structure

• Have created field maps for a single coil misplaced by five steps in:– -1° < pitch < 1° – -4° < roll < 4° – -1° < yaw < 1° – -2 < r < 2 cm– -10 < z < 10 cm– -5° < φ < 5°

Axes in frame of single coil


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Slopes give, for example,

Then , the uncertainty in z allowed

What are the relevant ,, ,

Our ability to determine in that septant may also be important.

We’ll measure a certain rate R and asymmetry A in each septant. We assume the allowable uncertainty on A to be 0.1 ppb

Sensitivity Studies


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Asymmetry vs. position offset

Asymmetry vs. rotation offset


Preliminary Results

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Fit to plots is given by

in range where approximately linear

Mean Asymmetrya (ppb) b

Z 31.75 -0.01 ppb/cmR 31.75 0.34 ppb/cmT 31.74 -0.01 ppb/degree

Roll 31.72 0.04 ppb/degreeYaw 31.75 0.06 ppb/degreePitch 31.77 -0.13 ppb/degree

= -9.24cm = 2.94mm = -17.86°

= 2.28° = 1.59° = -0.75°

where

Then, for example,

(>10 cm over magnet length)

What about physical constraints?


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Closest approach


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Summary• These results have some simulations with same random seed

(statistical uncertainty is not as good as it seems)– Need to re-run those simulations and redo the results– All plots vs. offset treated as linear, though some clearly are not

• Very preliminary results show order ~3 mm sensitivities (not sub-mm)

• Need to look at the effect of tracking algorithm with incorrect maps

• What is the most important parameter – what is it that will determine the sensitivity – A background correction done incorrectly?– The mean asymmetry, as I’ve assumed here?– The mean θlab, which will go into the extraction of sin2θW?


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Neutron shielding


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Radiation dose


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Support Structure


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Frame Design


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Vacuum Chamber design


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Cut away views


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Stress and deformation analysis


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Bids?


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Extra Slides


24(Rate weighted 1x1cm2 bins)

Tracks in GEANT4 for nominal field

Mollers

eps


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Slopes give, for example,

Then , the uncertainty in z allowed

What are the relevant ,, ,

We’ll measure a certain R and A in each septant. What matters is our ability to determine in that septant.

𝑄2=4𝐸𝐸 ′ 𝑠𝑖𝑛2𝜃𝑙𝑎𝑏

2

𝛿𝑄2=( 𝜕𝑄2

𝜕𝐸 )2

(𝛿𝐸 )2+( 𝜕𝑄2

𝜕𝐸 ′ )2

(𝛿 𝐸 ′ )2+( 𝜕𝑄2

𝜕𝜃 𝑙𝑎𝑏)2

(𝛿𝜃𝑙𝑎𝑏 )2


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Assuming

𝛿𝑄2=( 𝜕𝑄2

𝜕𝐸 )2

(𝛿𝐸 )2+( 𝜕𝑄2

𝜕𝐸 ′ )2

(𝛿 𝐸 ′ )2+( 𝜕𝑄2

𝜕𝜃 𝑙𝑎𝑏)2

(𝛿𝜃𝑙𝑎𝑏 )2

The uncertainty on is:

~ 0.001 GeV ~ 0.001 GeV

~ 1.33 GeV2/rad

𝛿𝑄2

1.33𝐺𝑒𝑉 2/𝑟𝑎𝑑=𝛿𝜃𝑙𝑎𝑏=

(0.005 ) ( .0058GeV 2 )1.33𝐺𝑒𝑉 2/𝑟𝑎𝑑

=2×10−5𝑟𝑎𝑑

zcoll = 590cm

ztarg,up = -75cmztarg,center = 0cmztarg,down = 75cm

θlow = 5.5mradθhigh = 17mrad

Rinner = 3.658cmRouter = 11.306cm

From center: From downstream:

θlow,cen = 6.200mrads θlow,down = 7.102mradsθhigh,cen = 19.161mrads θhigh,down = 21.950mrads

Finite Target Effects

Rinner

Router

ztarg,downztarg,up ztarg,center

θlow,up

θlow,down

θhigh,up

θhigh,down

Assume 5.5 mrads at upstream end of target, instead of center


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Looking downstream

x

y

φ=-360°/14

φ=+36

0°/1

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B

r

φIn this septant:

By ~ Bφ

Bx ~ Br

By

Bx ByBx


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GEANT4• Moved to GDML geometry description• Defined hybrid and upstream toroids• Parameterized in same way as the TOSCA models


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GEANT4 - Collimators


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GEANT4 – Acceptance definition

MOLLER Spectrometer Update

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