From ernie@physics.carleton.ca Fri Sep  5 15:20:40 2003
Date: Tue, 2 Sep 2003 12:55:26 -0400 (EDT)
From: Ernie Neuheimer <ernie@physics.carleton.ca>
To: Madhu@physics.carleton.ca
Cc: Kirsten Sachs <sachs@physics.carleton.ca>
Subject: Measurement of Dupont Kapton XC Film Resistance with Applied
    Voltage.
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   Madhu,

	  As requested I measured the resistance of the Kapton XC
	film you have been using in the Micromega detectors.
	I believe this film to be the Dupont part #100XC10E7, i.e.,
	10 MegOhm per square, 1 mil thick, carbon particulate loaded
	Kapton.

	  Five strips each 2cm wide and effective length 24cm were
	mounted on a paper surface with the usual ~1.2cm x 2cm
	copper tape (conductive through adhesive contacts, to which
	were soldered light flexible wire terminals for electrical
	connections. The copper tape contact areas to the film were
	each burnished or rubbed with a round point to minimize
	contact resistance. Thus these strips were 12 squares long.

	  Applied voltage to the strips ranged from 1V to 3000V
	and was measured by a Keithley model 2000 DVM to 1000V
	and the same instrument with a 1000:1, 1% HV divider for
	voltages above 1000V. Current in each strip was measured
	by another Keithley DVM connected as ammeter in series
	with the strip only, thus the current of the voltmeter
	was not part of the strip current measurement.

	  Tabled below are the measured currents at the applied
	voltages:

	Voltage:	Measured Currents (microAmp.):	
	(volts)
	   	Strip #1:  Strip #2:  Strip #3:  Strip #4:  Strip #5

	   1	  0.13	    0.12	0.13       0.13	      0.12
	   2	  0.30	    0.29	0.28	   0.28	      0.29
	   5	  0.78	    0.78	0.76       0.76	      0.78
	  10	  1.59	    1.59	1.54	   1.56	      1.60
	  20	  3.21	    3.22	3.14       3.16       3.23
	  50	  8.07	    8.12	7.92       7.96       8.11
	 100     16.24	   16.37       15.96	  16.03	     16.37
	 200     32.8	   33.15       32.29      32.45      33.10
	 500     84.3	   85.40       83.37      83.77      85.21
	1000    175.8	  178.5	      174.5      175.08     177.9
	2000    377.3	  383.2       374.7      376.2	    381.5
	3000    605.4*	  614.*       601.2*     602.7*     611.4*

	* At these higher field strengths the current was slowly
	  increasing. Measurements were taken after about three
	  seconds after voltage was applied.

	  It will be noted that measured currents at applied voltages
	are remarkably similar from strip to strip.

	   The surface resistance per square was calculated using the
	average strip current at an applied voltage and these values
	are tabled below: 


	Applied 12	Calculated Total
	Square Strip	12 Square Avg. 
	 Voltage:	 Resistance:
	  (Volts)	  (MegOhms)

	   1		   8.0
	   2		   6.9
	   5		   6.5
	  10		   6.35
	  20		   6.27
	  50		   6.22
	 100		   6.18
	 200		   6.11
	 500		   5.92
	1000		   5.67
	2000		   5.28
	3000		   4.94

	Applied		 Calculated 
	Voltage	         Resistance
	per Square:      per Square:
	 (Volts)	 (Meg Ohms)

	   1/12		  0.666
	   2/12		  0.575
	   5/12		  0.542
	  10/12		  0.529
	  20/12		  0.523
	  50/12		  0.518
	 100/12		  0.515
	 200/12		  0.509
	 500/12		  0.493
	1000/12		  0.473
	2000/12		  0.440
	3000/12		  0.412

	  A plot of the variation of surface resistance with
	applied voltage will be attached to this report
	presented at the next TPC meeting.

					Ernie.