Download 2 - DORAS

pressure gauge ports and is attached by means of an adjustable mount to the carriage
assembly. The carriage assembly utilises a recirculating ball bearing system, assuring
smooth and accurate movement over the entire tracking range.
Correct angular
orientation of the scanning detector assembly to the beam is maintained through all
wavelengths by a straight edge bar.
The bar is built in an upside down "U"
configuration and houses the wavelength drive screw. A manual scanning knob and
mechanical counter assembly is attached to the end of the precision drive screw and
straight edge assembly. Rotation of the knob moves the multichannel detector
assembly along the Rowland circle. The mechanical counter reading is graduated in
inches and indicates the chordal distance from the centre of the grating to the
approximate centre of the detector array. The detector chamber can be moved across
the Rowland circle, i.e., perpendicular to the point of tangent, via an adjustable
translation stage. The adjustment is controlled by means of a micrometer and two
locking screws. Loosening one screw and tightening the other screws moves the
detector across the circle. An isolation valve is located between the detector chamber
and the metal bellows. A support frame has been designed to carry cooling lines to
the detector system which clamps onto the detector chamber. A stainless steel o-ring
sealed bellows connects the detector scanning assembly and the main vacuum
chamber which contains the grating.
Angle ol Incidence a
F ig u r e 2 .3 P lo t o f th e v a r ia tio n o f b la z e w a v e le n g th
(A) w ith
a n g le o f
in c id e n c e f o r th e 1 2 0 0 lin es p e r m m g r a tin g u sed in th is s e t o f
e x p e rim e n ts [K ie r n a n 1 9 9 4 ].
Range o f B ellow s
600 500 -
400 •
300
200
0
4
S
12
16
20
24
28
32
36
Chordal Distance (inches)
F i g u r e 2 .4 P lo t o f th e w a v e le n g th r a n g e s p ossib le w ith a 1 2 0 0 lin es p e r
m m g r a tin g a t an g les o f g r a z in g in c id e n c e fr o m 8 2 ° to 8 8 ° [K ie r n a n
1 9 9 4 ].
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