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 Coil	Solenoid Mode	Gradient Mode
Physical Parameters
Active Coil Package Length [mm]	250	640	640
Location of the Peak B Point on the Axis [mm]	±195	±105	±240
Electrical Parameters
Magnet Design Current I_d [A]	270	230	265
Probable Short Sample Quench Current [A]	not known	286	323
Design Margin along the Load Line at 4.2 K	not known	0.803	0.821
Induction on Axis at I_d at R=0 and Z=0 [T]	~3.24	4.99	0.00
Maximum Induction on Axis at I_d [T]	4.64	5.04	3.48
Maximum Induction at R=20 cm at I_d [T]	not known	5.85	5.13
Maximum Induction in the Coil at I_d [T]	not known	6.82	6.52
Maximum Gradient on Axis Z=0 at I_d [T/m]	-NA-	-NA-	24.0
Coil Average Current Density at I_d [A/mm²]	150.55	128.24	147.76
S/C Matrix Current Density J at I_d [A/mm²]	171.34	145.96	168.17
Magnet Self Inductance [H]	41.67	98.22	68.46
Magnet Stored Energy E at I_d [MJ]	1.519	2.598	2.404
EJ² Limit for the Magnet at I_d [J A²/m⁴]	4.46x10²²	5.54x10²²	6.78x10²²

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], B_z[T], B_r[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