PHYSICS 225, 2 ND YEAR LAB
-
Upload
trevor-henry -
Category
Documents
-
view
14 -
download
0
description
Transcript of PHYSICS 225, 2 ND YEAR LAB
![Page 1: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/1.jpg)
PHYSICS 225, 2ND YEAR LAB
VACUUM TECHNOLOGY
G.F. West
Thurs, Jan. 12
![Page 2: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/2.jpg)
INTRODUCTION
Humans work in a gaseous environment.
Although less dense than solids or liquids, the normal gas environment greatly influences much physics.
Often, to do interesting and important physics, one must get rid of it.
![Page 3: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/3.jpg)
WHAT IS A VACUUM ? The absence of appreciable matter (i.e., atoms,
molecules, ions, particles), usually as gas.
How do we measure the amount of gas? As mechanical pressure on container walls or
neighbouring gas.
Pressure = Force /unit area = N/m2= Pa (SIU);
= bars (cgs)
= psi (USA/Imperial);
= Atm (Chem);
= mmHg = Torr (traditional physics);
![Page 4: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/4.jpg)
KINETIC THEORY OF GASSES (The colliding billiard ball model ) Gas atoms have a range of velocities,
increasing with temperature. Gas molecules therefore have appreciable
energy and momentum. Pressure is the cumulative result of the
momentum changes in collisions. Collision likelihood is usually expressed
as “mean free path” (average distance molecules move between collisions).
![Page 5: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/5.jpg)
LEVELS OF VACUUM
Air at 273 K, molecular Vrms ~ 485 m/s Pressure (V HV UHV UHV ) Atm, 1.0 1/760 - - - - kPa, 101.3 0.13, 0.13Pa - - - psi, 14.7 0.02 - - - - Torr, 760 1 1e-3 1e-6 1e-9 1e-12 Mean Free Path, at 273 K, mol radius 0.3 nm; m ~1e-7,~7e-5,~7e-2, ~7e+1,~7e+4, ~7e+7
![Page 6: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/6.jpg)
VACUUM PUMPS Mechanical; with valves, vanes, diaphrams (Roughing pumps, forepumps). Entrainment principle
Diffusion pumps, Turbomolecular pumps.
Entrapment principle Cryopumps, ionpumps (gettering) TI sputtering molecular sieves (zeolites and other synthetic
microporous compounds)
![Page 7: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/7.jpg)
PROBLEMS WITH PUMPING
Need for a forepump.
Contamination of vacuum by backflow.
Gas selectivity.
Need for regeneration.
Virtual leaks.
Speed, ease of cycling to lab conditions.
![Page 8: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/8.jpg)
VAPOUR PRESSURE
![Page 9: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/9.jpg)
MULTI-PUMP SYSTEM
![Page 10: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/10.jpg)
ROTARY VANE FORE PUMP
![Page 11: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/11.jpg)
DIFFUSION PUMPS
![Page 12: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/12.jpg)
TURBO-MOLECULAR PUMPS
![Page 13: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/13.jpg)
TURBO-MOLECULARPUMP
Specifications
MDP 5011
Pumping speed (L/s N2) 7.5
Ultimate pressure (Torr) 7.5 x 10-7
Compression ratio:
......N2 1 x 109
......He 2 x 104
......H2 1 x 103
Speed (rpm) 27,000
Max. ambient temp (°C) 50
Exhaust flange QF16
Pump weight (lb) 5.5
Power supply (VAC) 115
Other voltages available on request
![Page 14: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/14.jpg)
ION PUMP
![Page 15: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/15.jpg)
ION VACUUM GAUGE
![Page 16: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/16.jpg)
THE VACUUM ENCLOSURE
Materials: -
(Glass & stainless steel predominate.) Requirements:-
Chemically inert Cleanable Bakeable Strong Workable, (e.g., machineable)
![Page 17: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/17.jpg)
TYPICAL VACUUM SYSTEM Forepump Main vacuum pump with cooling. Gate valve,(to allow pump turn off). Vacuum gauges, if not intrinsic to pumps. Cold trap(s) (Liquid air). Sample inlets, if required. View & manipulation ports, experiment
area. Bakeout system.
![Page 18: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/18.jpg)
VACUUM SYSTEM COMPONENTS
Older systems mainly were hand fabricated from glass by artisanal glassblowing.
New systems mainly are constructed from commercially manufactured stainless steel components using (e.g.,):- Bolted flange connections Thin metal seals Glass- to-metal sealed electrical connections Bellows connected or in-vac bakeable manipulators Special window glasses for radiation entry/exit
![Page 19: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/19.jpg)
VACUUM COMPONENTS
![Page 20: PHYSICS 225, 2 ND YEAR LAB](https://reader036.fdocuments.in/reader036/viewer/2022070401/56813691550346895d9e1a82/html5/thumbnails/20.jpg)
USES OF VACUUM TECHNOLOGY
Semiconductor lithography and surface coating. Analytical inst’s; e.g., spectrometers, microscopes. Particle accelerators, HEP Space simulation Nanotechnoloy Surface physics. Gas lasers. Manufacturing of special materials.
Some examples:-