JR Macdonald Laboratory 1998 Summer Short Course:

	Introduction to Vacuum Physics and Technology:	
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      Problem 4.1) A differentially pumped gas target has
	0.1" diameter beam entrance- and exit apertures. It is
	mounted in the center of a 4" 4-way cross (4x3.75"
	long). It is sealed with 4.5" x .1" Buna-N O-rings. The
	differential pumping is accomplished with a TPU400
	turbomolecular pump (6" inlet port). The TPU400 is
	adapted to 4" with a zero-length reducer and connected
	with a 7.5" long, 4" diameter nipple to the 4 way
	cross. The TPU400 pump is backed by a DUO4A rotary vane
	pump. A hydrogen gas flow is adjusted to maintain 0.1
	Torr in the target region. 
	a) What is the expected hydrogen foreline pressure? 
	b) What is the expected pressure in the differential
	   pumping region? 
	c) What are the expected pressures in the foreline and
	   in the differential pumping region if the DUO4A is
	   replaced with a DUO30A? 




      Problem 4.2) What are the expected residual gas
	components and their ultimate partial pressures in the 
	differentially pump gas target of 4.1? 




      Problem 4.3) Design and make mechanical drawings for a 
	O-ring sealed motion feedthrough with a 1/2" rod on a 
	2.75" CF flange, using a 1/2"I.D. 0.139" O-ring.