Faraday Cup Measurment Notes » History » Revision 3
Revision 2 (Jim Pulokas, 10/04/2010 03:30 PM) → Revision 3/11 (Jim Pulokas, 10/04/2010 04:34 PM)
h1. Faraday Cup Measurment Notes Picoammeter setup: * plug in * wait 1 hour * activate ZCHK (maybe already when turned on) (should say ZC on screen) * plug into faraday holder * set to lowest range (2nA) * activate ZCOR to set zero (should say ZZ on screen) * set auto range if desired * deactivate ZCHK to begin measuring * focus beam to a spot * pull out holder until spot hits the faraday cup (max current) ** 200keV *** 1.01 1.00 nA ** 120 keV *** 2.53 nA h1. Exposure Time to Screen Current measurment * refer to Tecnai Help for "Exposure Time, Plate Camera CP" * formula: beam current (nA) = 2.15 * emulsion / measured_exposure_time ** exp time is between 3.1 and 3.5 depending on size of beam ** emulsion = 1 ** beam current is between 0.61 and 0.69 nA h1. Leginon screen scale factor measurement * adjust scale factor until beam current is same as faraday cup ** 200 keV *** 0.725 ** 120 keV h1. Camera sensitivity ** 200 keV *** 45-50 count/e ** 120 keV *** 107 count/e