G-2 Tour Notes

Map of the Building Relative to the High Rise



Brendan Kiburg (217-721-3956)
Dee Hahn (630) 840-2354

Building Access

IMPORTANT: Nobody with medical issues (pacemaker or similar) allowed in the hall. Tours must not cross the yellow lines painted on the catwalk in the main hall due to field hazards. This means no use of the staircases.

Your badge will allow you access to MC-1 after reviewing building hazards and completing this quick hazard awareness training: . The reason you need to take the training is because the conditions are changing during this construction and work may even occur on the weekend tour dates. Upon completion of this training, please notify so that we can ensure your badge will approved.

General Hazard awareness
  • Closed-toed shoes.
  • No magnetic materials are to be brought into/left in the hall.
  • The cryo room is an ODH-1 area so the tour does not go into it. You can look through the windows.
  • The main hall is an ODH-0 area (no training needed, but if the alarm goes off you should calmly exit through the front door)
  • The tornado shelter is in the power supply room, adjacent to the elevator.
  • The building is monitored by video and motion sensors, so actions may be recorded.
  • Do not enter the pit when the crane is in operation.
  • Reminder: In an emergency call x3131

General Tour Flow

I generally start by giving them an overview of the goals of the precision measurement, then show them the facility (cryo room, mechanical room, posters in the mezzanine, control room, computer room) and then finally bring them into the experimental hall to discuss the transport and the apparatus.

Building Entrance - How do Muons Probe the Universe? - (poster that aids the flow for the tour guide)
  • Describe the muon, how we understand it well, and how that enables us to use it in precision experiments as a probe
  • Describe spin (reference tops, gyroscopes,etc)
  • Ask what we mean by the vacuum. How does a physicist view the vacuum (e.g. virtual particles, quantum foam etc)
  • Describe how the muon's spin precession is affected by the quantum world
  • Discuss the name g Minus 2. Dirac says g=2, quantum world makes it a little different, hence the "anomalous magnetic moment"
  • The difference between the effects of known particles and what we measure is attributed to new particles popping into the vacuum
  • Previous experiment showed 3.6 sigma discrepancy, want to reduce the uncertainties and see if the discrepancy persists
  • 20 times as much data, factor 2 improved systematics --> factor 4 reduced error bars
  • Describe mu2e as an alternative way to use this probe
  • muon to electron conversion without any neutrinos
  • in the presence of a nucleus. Ask them why? (answer: conservation of momentum/energy--the lighter electron needs to recoil against something else since there are no neutrinos here)
  • charged lepton number conservation (empirically observed but also theoretically predicted at a very deep level)
  • SM says rate µ -> e conversion is 10^-54 through neutrino emittance-->oscillation--> absorption
  • If we see it happen, there must be new particles that can mediate this reaction
Cryo room
  • ODH-1 area, can look through the windows (don't enter)
  • Two refrigerators (cryo-coolers?) for muon g-2, two for mu2e
  • Liquify helium for cooling
  • Why do we need that? Superconducting magnets (should have come across this in other tours).
    • Ask about the difference between passing current through a superconductor and a lightbulb (thermal losses due to resistance)
    • Superconducting coil in medical MRI only needs to be charged once a year
  • Whats the temperature? ~4K
Mechanical room
  • Power supplies for g-2 magnets and equipment
  • Holes in the wall that go outside for mu2e magnet power supplies
  • Weather and construction permitting, open the door and describe the tunnel that will carry protons to the mu2e experiment
  • Point out multipurpose nature of the building (Muon Campus)
  • Might point out the boil-off vent for LN2 (filled ~weekly)
Upstairs to the Mezzanine (goal here - use posters to explain the 2 measurements, muon precession frequency and magnetic field)
  • Straw tracker station is setup plus there are two posters explaining it
  • Watch the positrons from muon decay, extract trajectories
  • muon precession comes from a_mu and B Field. Have to control the b field and measure what it is to better than 1 part in a million
  • really need to know where the ensemble of muons decayed from
  • tracker helps us understand muon distribution
  • Move onto the posters of the ring move
  • superconducting (Niobium-Titanium) coils, 5200 Amps per turn
  • Makes 1.5 Tesla field (roughly the same as you would feel in an MRI magnet at a magnetic facility)
  • 750 tons steel in a "C" shape steers the field lines it produces.
  • Very expensive (was largest superconducting magnet when built in 1990s), ~ $30 million in today's dollars to make
  • Much more efficient to move it instead
  • Needed to keep fragile device from twisting or flexing (think potato chip or saddle). Spec: hold flat within 3 mm over the 14 meter diameter
  • Show poster that has the full ring move (disassembling, barge, trailer, full route, installation into building, reassembly)
  • Why can't you cut the ring into parts to move? (The superconducting coil is a mile-long continuous loop of wire. If you cut it you would need to weld it back together. This would create sites for superconducting shorts.)
  • When the ring was on trucks the maximum speed was 10mph
Back downstairs
  • Control room - monitor cryo, controls, look at plots of diagnostics of detectors, etc
  • Final room is computer room - data streams in here and is stored to tape
  • Expect several PB of data
Experimental Hall
  • Hazard reminder (watch your steps)
  • Students are not supposed to bring anything in (bags, phones, wallets etc), so point out the little cubby by the entrance to the hall.
  • Stay on the catwalk overlooking the ring -- useful to think about it like a clock for describing things. Define far side as 12 o'clock (as viewed from above)
  • Ask where beam comes from (answer: door in the back left corner will have a beamline coming through it, between 10 and 11 oclock)
  • Where does beam enter storage ring? 12 oclock -- discuss inflector and how it cancels the fringe field allowing the muon beam to come in “straight"
  • Muons are on “wrong circle” — they would go around and then run back into the pipe they came in through. Need to give it a kick of 7cm. Use a “kicker” at 3 o’clock
  • How long is muon train? 120 ns (~10,000 muons) - have to kick for this length, at the right time
  • How fast do muons go around? 149 ns (single train fills about 4/5ths of the ring)
  • How long do muons live? 2.2 microseconds (millionths of a second) —> 64 microseconds with the time dilation gamma of 30 -> ~few hundred orbits of the ring before decay
  • Experimental hall is temperature stable to +/- 1 deg C. This is important because steel expansion of 10^-5 to 10^-6 m per deg C. Steel expansion would change the B-field
  • Insert very thin steel shims (~1 mil) to homogenize the magnetic field
  • Make field uniform Spring 2015 through Winter 2015 (9 months)
  • Install vacuum chambers
  • Install calorimeters, trackers, electronics 2016
  • Accelerator in parallel, brining muons in at end of 2016, start of 2017

G-2 Tour Notes

There are many posters in the MC-1 Building on the transport, how muons probe the universe, g-2 computing, g-2 trackers and g-2 calorimeters

Recent map of route to MC1 building (home of muon g-2 electromagnet) from Wilson Hall