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