Subject: New DIS Quartz Slits (sknapp; 11June 96)

From: Steve Knapp

Submitted: Tue, 11 Jun 1996 10:57:21 -0600

Message number: 18 (previous: 17, next: 19 up: Index)

New DIS Slits.  [Best read in fixed width font.]

We have received new aluminized quartz slits for DIS.  The slit widths 
have been measured using the measuring engine at the Solar Observatory, 
with mean values of:

    211 (+- 4)    and    274 (+- 7)  microns   (both N = 3, small samples)
or  1.24          and    1.61        arcsec.

The goal was to obtain slits with widths of 2.1 and 3.0 arcsec.  The slits 
were manufactured from and replace the previous (0.47 and 0.87 arcsec) 
quartz slits.  They were produced by Don Loomis using wire-shadow fixtures 
made earlier by Mike Carr and the aluminizing was done by a sub-contractor.  
APO supplied the fine piano wires.  It is believed that the undersized slits
were the result of the aluminizing setup at the subcontractor; the ballistic
trajectories of the Al probably were not all near normal to the quartz plates,
quite likely if the subcontractor had several jobs in the vacuum chamber.
I regret that we did not obtain a 2 arcsec slit this time.  I suspect, 
however, that at least the 1.61 arcsec slit will see service straight away.
We are pursuing other sources (including our own aluminizing at the Solar 
Observatory) for additional slits.

For the record, here are some quantitative and qualitative observations of the
new slits (which I will call the "1.2 arcsec" and "1.6 arcsec" slits):

Provisional Name      "1.2 arcsec"                  "1.6 arcsec"

Mean slit width, s    211 microns = 1.24 arcsec     274 microns = 1.61 arcsec
Standard dev (N = 3)    4 microns                     7 microns

Quartz plate w x h    1.860 x 2.995 inches          1.865 x 2.996 inches
                      4.724 x 7.607 cm              4.737 x 7.610 cm

Thickness of plate    0.0624 to 0.638 inch          (Not measured, assumed same)

Curvature of slit,    17 microns approx.            14 microns approx.
(peak displacement  
of slit from straight 
line in the central 
5 cm of slit length)

Edge irregularities   Clean, nothing obvious        Clean, nothing obvious

Edge sharpness        No "penumbra" observed in transmission, both slits

I guesstimate the accuracy of a single measurement with the engine at around 
6 microns.

Steve Knapp   11 June 1996
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