MTA Magnet

The superconducting test magnet at the MTA was designed and built at LBNL and Wang NMR and first used for the 805MHz rf test program at Fermilab's Lab-G. It has two coils that can be powered with equal (solenoid mode) or opposite (gradient mode) polarity. Each coil is 250mm long with inner/outer radii of 260/321mm and the gap between the coils is 140mm. During rf tests in Lab-G in the past, we typically operated in solenoid mode at up to 2.5T (~120A coil current). The magnet looks like this from (left to right) the top, the front and in side cross section:

Detailed specs for the magnet as well as results for pressure tests, electrical and magnetic measurements and initial quench history are given in MC-Note 163 (also LBNL-45148) by Mike Green. The basic parameters are reproduced below:

Single CoilSolenoid ModeGradient Mode
Physical Parameters
Active Coil Package Length [mm] 250640640
Location of the Peak B Point on the Axis [mm] ±195±105±240
Electrical Parameters
Magnet Design Current Id [A] 270230265
Probable Short Sample Quench Current [A] not known286323
Design Margin along the Load Line at 4.2 K not known0.8030.821
Induction on Axis at Id at R=0 and Z=0 [T] ~3.244.990.00
Maximum Induction on Axis at Id [T] 4.645.043.48
Maximum Induction at R=20 cm at Id [T] not known5.855.13
Maximum Induction in the Coil at Id [T] not known6.826.52
Maximum Gradient on Axis Z=0 at Id [T/m] -NA--NA-24.0
Coil Average Current Density at Id [A/mm2] 150.55128.24147.76
S/C Matrix Current Density J at Id [A/mm2] 171.34145.96168.17
Magnet Self Inductance [H] 41.6798.2268.46
Magnet Stored Energy E at Id [MJ] 1.5192.5982.404
EJ2 Limit for the Magnet at Id [J A2/m4] 4.46x10225.54x10226.78x1022

The magnet is powered by a 2.5kW EMS-7.5-300 (7.5V 300A) power supply.

Plots of the on-axis field can be found here.

Approximate field maps are available for the solenoid and gradient modes in text format (z[mm], r[mm], Bz[T], Br[T]). z=0 is the center of the magnet warm bore.

You can also get approximate contours for noflip-2.5G, flip-2.5G, noflip-300G, and flip-300G.

Yağmur Torun September 15, 2006