JR Macdonald Laboratory 1998 Summer Short Course:

	Introduction to Vacuum Physics and Technology:	
	----------------------------------------------

	Problem #3: 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 DUO30A rotary vane pump. 

	Question A:
	What is the expected pressure in the differential
	pumping region if the gas target is kept at 0.1
	Torr Nitrogen ? 

	Question B:
	What is the expected pressure in the differential
	pumping region if we eliminate the 7.5" long 4"
	diameter nipple? 

	Question C:
	What is the expected pressure in the differential
	pumping region if the gas target is operated with
	0.1 Torr Hydrogen?