Faraday Cup Measurment Notes » History » Version 4
Jim Pulokas, 02/02/2011 01:02 PM
| 1 | 1 | Jim Pulokas | h1. Faraday Cup Measurment Notes |
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| 2 | |||
| 3 | Picoammeter setup: |
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| 4 | * plug in |
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| 5 | * wait 1 hour |
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| 6 | * activate ZCHK (maybe already when turned on) (should say ZC on screen) |
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| 7 | * plug into faraday holder |
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| 8 | * set to lowest range (2nA) |
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| 9 | * activate ZCOR to set zero (should say ZZ on screen) |
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| 10 | * set auto range if desired |
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| 11 | * deactivate ZCHK to begin measuring |
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| 12 | 3 | Jim Pulokas | * focus beam to a spot |
| 13 | * pull out holder until spot hits the faraday cup (max current) |
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| 14 | ** 200keV |
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| 15 | *** 1.01 nA |
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| 16 | ** 120 keV |
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| 17 | *** 2.53 nA |
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| 18 | 2 | Jim Pulokas | |
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| 20 | h1. Exposure Time to Screen Current measurment |
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| 21 | |||
| 22 | * refer to Tecnai Help for "Exposure Time, Plate Camera CP" |
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| 23 | * formula: beam current (nA) = 2.15 * emulsion / measured_exposure_time |
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| 24 | ** exp time is between 3.1 and 3.5 depending on size of beam |
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| 25 | ** emulsion = 1 |
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| 26 | 1 | Jim Pulokas | ** beam current is between 0.61 and 0.69 nA |
| 27 | 3 | Jim Pulokas | |
| 28 | h1. Leginon screen scale factor measurement |
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| 29 | |||
| 30 | * adjust scale factor until beam current is same as faraday cup |
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| 31 | ** 200 keV |
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| 32 | *** 0.725 |
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| 33 | ** 120 keV |
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| 34 | |||
| 35 | h1. Camera sensitivity |
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| 36 | |||
| 37 | ** 200 keV |
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| 38 | *** 45-50 count/e |
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| 39 | ** 120 keV |
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| 40 | 1 | Jim Pulokas | *** 107 count/e |
| 41 | 4 | Jim Pulokas | |
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| 43 | |||
| 44 | h1. 2011-02-02 Tecnai 2: |
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| 45 | * faraday measurement: 1.52 nA |
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| 46 | * Tecnai main screen measurement (emulsion = 1): 2.15 / 2.6 = 0.83 nA |
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| 47 | * Leginon scale factor to match faraday current: |