Mu2e Magnet Design Changes

Michael Lamm

for the Mu2e Collaboration

and TD/Magnet Systems Dept.

March 26, 2012All Experimenters Meeting 1

Contributors to the Mu2e Solenoid Design:

N. Andreev, G. Ambrosio, R. Bossert, J. Brandt, M. Buehler, R. Coleman, D. Evbota, W. Jaskierny, V.V. Kashikhin, M. Lopes, J. Miller, T. Nicol, D. Orris, R. Ostojic, T. Page, T. Peterson, J. Popp, V, Pronskikh, Z. Tang, M. Tartaglia, Z. Tang, M. Wake, R. Wands and R. Yamada

2

ProductionSolenoid

TransportSolenoid

DetectorSolenoid

ProductionTarget Collimators

StoppingTarget Tracker Calorimeter

protons

2.5T4.6T

2.0T

1.0T

e

Mu2e experiment consists of 3 solenoid systems:

Measure the Rare Process: - + N e- + N

Muon timing is important.Negative axial field gradients prevent unwanted trapped particles from entering “Search Window”

March 26, 2012All Experimenters Meeting 3

Reason for Design Changes

• Recommendations from May 2011 Independent Design Review

– More operating margin for PS

– Simplify DS

– Better mechanical support for PS coils

• Value Management exercise in Fall 2011– Reduce cost of Solenoid project by ~$20M

• Change in requirements– Field requirements have become less stringent with

detailed beam studies Simplify magnet designs

L2 Solenoid

Feedboxes

Distribution Lines

TS4-5Cryostat

TS3 Cryostat

TS1-2 Cryostat

DS Cryostat

PS cryostat

• Power Supply/Quench Protection• Cryoplant

PS IRON

DS IRON

• Field Mapping • Ancillary Equipment• Insulating vacuum• Installation and commissioning

• Production Solenoid (PS)• Transport Solenoid (TS)• Detector Solenoid (DS)• Cryogenic Distribution

OFF PROJECT

Single Layer-shorter Spectrometer

4.6 T peak field Less layers for PS

DOWN SCALEDDOWN SCALED

Changes Since May 2011 IDR

4

PS Baseline Design Changes

All Experimenters Meeting5

Iron Return YokeCryostat Wall

• Peak field 5T- I operation ~10kA• NbTi Rutherford cable + Ni doped

aluminum stabilizer (like ATLAS CS)

• Indirect Cooling (Thermal Siphon)• Hadron absorber intercepts beam

secondaries– ~20 Watts deposited in coils

• Nominal peak field 4.6T– 5T still possible with reduced

margin

• Reduce number of layers• Thinner conductor (lower current)• Remove iron yoke

Gradient made by 3 axial coils same turn density but change # of layers

Wound on individual bobbins

PS Field vs. Tolerance Bands

All Experimenters Meeting March 26, 2012 6

Meets 5% field uniformity spec

March 26, 2012All Experimenters Meeting 7

Collaboration with Japan

Fabrication of practice PS coil at Toshiba (4 Layer/8 Turns)

Uses aluminum stabilized NbTi conductor from Hitachi Cable

Coil will be later tested at Fermilab

New baseline Transport Solenoid

TS1

TS2

TS4

TS5

•ThreeTwo cryostats: TSU, TSD

•TS3: TS3U, TS3D. Wider coils to compensate for gap

Rotatable Collimator, P-bar window

G. AmbrosioTS Leader

•New coil fabrication proposed for better mechanical support.

All Experimenters Meeting March 26, 2012 8

•TS1,TS3,TS5: Straight sections with axial gradient•TS2/TS4: approximate toroidal field•Accomplished by many thin solenoid rings of different amp-turns

Coil Fabrication

9

Bolted connections

Conductor

Al Outer Supports

March 26, 2012

• Original plan: use SS inner bobbins mechanical support complications.

• New plan: fabrication unit consists of two coils with outer support aluminum structure

• Coils wound on collapsible mandrel-then fit into outer aluminum ring

• Placement of coil in transport is determined by outer shell geometry

All Experimenters Meeting

TS Field Requirements

• All sections meet all requirements• Large margin wrt gradient requirement

March 26, 2012All Experimenters Meeting 10

Axial field distribution in the center of TS3 (left), axial gradient along TS3 (right).

Simplify DS Baseline

March 26, 2012

• OLD base line– Two coils: gradient + spectrometer bussed in series in a single cryostat– Two layer spectrometer, single mandrel field uniformity – Two layer gradient on single mandrel with aluminum spacers– Iron return yoke (not shown)

11All Experimenters Meeting

Spectrometer SectionGradient Section

Simplify DS Baseline

March 26, 2012

Spectrometer Section

Gradient Section

• New base line driven by relaxed field requirements– Modular coil design reduced cost/coil

– Spectrometer: 3 Single Layer Coils shorter coils, greatly reduced conductor volume, reduced field uniformity OK

– Original conductor cost estimate based on expensive PS conductor, smaller field DS requires smaller cross section, no need for special reinforced aluminum

– Relaxed calorimeter field requirements shorten spectrometer

12All Experimenters Meeting

DS Field vs. Tolerance Bands

March 26, 2012 13All Experimenters Meeting

Gradient Section Spectrometer Section

March 26, 2012All Experimenters Meeting 14

Conclusion

• Significant amount of work done prior to CD1– Conceptual design of solenoids

– Technology development with Japan

• Near term schedule– CD1 directors review April 3-5, Lehman review in June

– June 2012-2014• Test Toshiba coil/built prototype TS module/prototype conductor

– CD2 sometime in 2014• Order conductor/ Contract final design with industry

– Begin fabrication in 2016