# Polhe3 masing

## Yi's comment

You can calculate the current you need to create certain amount of field gradient given the geometry of the correction coils and the number of turns. The onset of the Masing effect depends on the polarization of the target and it is usually between 0-50 mG/cm. And the next is easy, and you just need to find a power supply which can provide enough current to cover that range to do perform a scan of the Masing effect threshold.

Intro to Masing effect: http://hallaweb.jlab.org/physics/experiments/he3/A1n/target/MASING_FAQ.html

Gradient coils for Transversity: https://hallaweb.jlab.org/wiki/index.php/Holding_Field_Control#Gradient_of_holding_field_.26_Correction_Coils

Tests of Masing effect during Transversity: http://hallaweb.jlab.org/halog/log/html/0902_archive/090225000436.html http://hallaweb.jlab.org/halog/log/html/0903_archive/090302124229.html http://hallaweb.jlab.org/halog/log/html/0902_archive/090225214605.html http://hallaweb.jlab.org/halog/log/html/0903_archive/090311195533.html there are more log entries

## Jie's calculation

THIS IS A ROUGH CALCULATE. But it can serve to set the current of gradient coil.

1. correction coil @1A

(left side is position away from target center) (right side is field, unit Gauss)

center 0G +-1cm 0.00752G +-5cm 0.0374G +-10cm 0.07372G +-20cm 0.13924G

average gradient along main field axis: 7.5mG/cm

WE can change current I to get the expected gradient I * 7.5mG/cm.

2. large coil Holding field @7.14A

center 23.036953G +-1cm 23.036953G +-5cm 23.035011G +-10cm 23.027242G +-20cm 22.918486G

average gradient along main field axis: 4~5.9mG/cm

(A. although I did not consider earth FIELD, this theoretical result seems to be small than 25G B. if we want to get 25Gauss, this theoretical calculating need current to be 7.74A C. our system are running current 7.14A now, I need to do further check)