TD Designs for mu2e Solenoid Magnets

Michael Lamm

for the Mu2e Collaboration

and TD/Magnet Systems Dept.

All Experimenters’ Meeting

January 25, 2010

January 25, 2010All Experimentors Meeting 2

What is Mu2e?• Measure the Rare Process: - + N e- + N relative to

- + N(A,Z) + N(A, X) – Goal: 4 orders of magnitude increase in sensitivity over previous

experiments• Strategy:

– Stopped muons in aluminum atom: high probability of interaction • Significant overlap of muon and nucleus wave functions

– Kinematically constrained - + N e- + N produces mono-energetic electrons

– Use lifetime of muon in atom to suppress “prompt backgrounds”• Out of time pions, p-bars, electrons in muon channel are a serious

problem

• Magnets role in Mu2e– Transport as many in-time, stoppable muons as possible– Prevent out of time other particles from reaching stopping target– Provide a uniform stable field for the final captured electron

spectrometer

January 25, 2010All Experimentors Meeting 3

Magnet System by Function

12206

25687

•Production Solenoid

8 GeV P•Transport Solenoid

•Graded field to collect conv. e- (2T1T)

•Uniform field for e- Spectrometer (1T)

e- Spectrometer

Production Target (PT) Central Collimator (CC) Stopping Target (ST)

ST

PT

CC

• Reflect and focus low P /’s into muon transport

• Strong Axial Gradient Solenoid Field 5T2.5T

•Sign/momentum Selection

•Negative Axial Gradient in S.S. to suppress trapped particles ~0.2 T/m

•Detector Solenoid

January 25, 2010All Experimentors Meeting 4

Magnet Procurement Strategy

Fermilab will act as a “General Contractor”:

• PS and DS will likely be built in industry– Need to develop a strong conceptual design and technical specifications

for vendors

– Final engineering design done by industry

– Similar strategy for most detector solenoids

• TS will likely be designed/built “in house”– Cryostat, mechanical supports built by outside vendors

– Coils wound in-house or industry depending on technology choice

– Final assemble and test at Fermilab

• Fermilab responsible for all interfaces and infrastructure– Significant magnet coupling between PS-TS and TS-DS

– Tight mechanical interfaces

– Cryoplant, power supplies, instrumentation…

January 25, 2010All Experimentors Meeting 5

MECO vs. Mu2e Magnet Concept

Copper Bar

SSC cable

MECO Mu2e switches to… why?

Coils 96 Solenoid Rings Continuous MandelLess Joints, Less Field Ripple,

smaller conductor volume

SC Conductor SSC Excess Cable* New High Current CableLess layers, smaller inductance:

benefits cooling and quench protection

Quench Stabilizer Copper Extruded Aluminum (PS/DS)Less nuclear heating, vendor

experience with modern detector solenoids

Cooling Scheme Bath Cooled (PS) and Conduction (TS/DS)

Conduction onlySimplify cryostat design.

Possible in PS with Al stab. and new cable

*100 km of cable lost between 2005-2008

January 25, 2010All Experimentors Meeting 6

PS DesignVadim Kashikhin

•Long continuous inner coils with several short graded outer “tunable” coils for gradient field and to “match into” transport•Benefits relative to Meco

•Reduce coil volume by 50% (Conductor Grading)

•Reduce inductance by x5 (Increased operating current)

•Reduce nuclear heating >x2 (Aluminum Stabilizer)

“Graded Conductor”

January 25, 2010All Experimentors Meeting 7

PS Magnetic DesignMeco Two layer Continuous Wind Shorter Version

Vadim Kashikhin

January 25, 2010All Experimentors Meeting 8

Temperature and Current Margins are Acceptable

0 1 2 3 4 5 6 7 8 9 10 110

250

500

750

1 103

1.25 103

1.5 103

1.75 103

2 103

2.25 103

2.5 103

2.75 103

SSL @4.50KSSL @6.17KIL load lineOL load lineIL operating pointOL operating point

Peak field (T)

Cri

tica

l cu

rren

t de

nsit

y in

SC

(A

/mm

^2)

0 1 2 3 4 5 6 7 8 9 10 110

2

4

6

8

10

12

14

16

18

20IL SSL @4.50KOL SSL @4.50KIL load lineOL load lineIL operating pointOL operating point

Peak field (T)

Cri

tical

cur

rent

(kA

)

Temperature margin > 1.5 K

6.17 K SSL

4.5 K SSL

Current Margin I/Ic = 65 percent

Current M

argin

Current M

argin

January 25, 2010All Experimentors Meeting 9

2 Coil PS - Al cable (RRR 1100 - 600) - 5Tmax - 1kV

0

2000

4000

6000

8000

10000

12000

0 20 40 60 80 100 120

Time (s)

Cu

rren

t (A

)

0

10

20

30

40

50

60

70

RRR1100 - Current

RRR600 - Current

RRR1100 - Temp

RRR600 - Temp

RRR = 600

RRR = 1100

Compare to copper stabilizer: peak temperature ~85Kelvin

Quench Protection: Aluminum Stabilized + High Current Mu2e PSC

oil Peak T

emp

(Kelvin)

Exc

itat

ion

Cur

rent

(A

)

Aluminum is an effective stabilizer

G. Ambrosio

January 25, 2010All Experimentors Meeting 10

DS Design (model after Atlas)

2 T 1 T gap 1T 1 T

0m 0.93m 2.4m 4.17m 10.9m 11.9m

240 162 117 90 turn/m at 9 kA 127

2 Tesla2.5 m Aperture5 meters long

1 Tesla1.8 m Aperture7 meters long

Atlas Solenoid

R. Yamada

2 1 Tesla1.8 m Aperture2.5 meters long

January 25, 2010All Experimentors Meeting 11

TS Design

• We are interested in building simplest, cost effective, most reliable TS Systems

• Questions• Confirm that coils met MECO spec (done)• Confirm that muon transmission is insensitive to

coil alignment (done)• How sensitive is spec to coil placement? (done)• Coil options. Building SS and/or Toroid coils as a

single graded solenoid (ongoing)• Do we need corrector coils (ongoing)

R. Coleman / M. Lopes

January 25, 2010All Experimentors Meeting 12

Collaboration with Japan

Vl. KashikhinN. AndreevA. Makarov

Technology Magnet to Study Aluminum Stabilized conductor

Aluminum Stabilized Conductor

Hitachi

Magnet Construction ongoing: Test in spring 2010

Conceptual Design

January 25, 2010All Experimentors Meeting 13

Conclusion

• Significant amount of work done prior to CD0– Design of PS and a bit on DS

– Technology development with Japan

• CD0 CD1– Complete the conceptual design + cost and schedule est….

• PS mechanical supports for coils; thermal model for conduction cooling with expected beam induced heat loads; long vs. short length tradeoff

• TS work with experiment to define collimator interfaces, coil technology choice

• DS mechanical supports for coils especially end forces