This document provides information about vacuum systems. It begins by defining vacuum and discussing the different levels or classifications of vacuum including rough, high, and ultra-high vacuum. It then explains various vacuum pump technologies used for different pressure ranges like rotary pumps, diffusion pumps, and cryopumps. It also covers vacuum measurement tools known as vacuum gauges and issues like leaks in vacuum systems. Overall, the document serves as an introduction to key concepts and components in vacuum technology.

1. Sagar Pandurang Kumbhar
Semiconductor Nanotechnology Lab (SNL)

2.  What is vacuum
 Classification of Vacuum
 Different Terminologies of Vacuum
 Pressure and Units of Pressure
 Vacuum Pumps
 Classification of Vacuum Pumps
 Vacuum Gauges
 Leak in Vacuum System
 Vacuum System
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3.  Vacuum is space void of matter
 Space with gaseous pressure much less than atmospheric pressure
 The word stems from Latin adjective vacuus for "vacant" or "void“
 Region with gaseous pressure less than atmospheric pressure
 Air is a gas mixture with approx. 1025 particles per m3
 Particles exert pressure or force on the walls of a defined space. The fewer particles there are in
the space, the lower the force exerted on the walls.
 Pressure = Force / Area
 100% vacuum would mean that there are no particles present
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4.  Dark energy
 Transiting gamma rays
 Cosmic rays
 Neutrinos
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5. To move a particle in a straight line over a large distance
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6. 6
 Why is a Vacuum Needed?
Contamination
(usually water) Clean surface
Atmosphere (High)Vacuum
To provide a clean surface

7.  Pressure is defined as force per unit area.
 The standard unit for pressure is the Pascal, which is a Newton per square meter.
 Evangelista Torricelli produced the first laboratory vacuum in 1643
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8. Vacuum
Rough
Ultra
High
High
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9. Rough
760~1x10-3
High
10-3 ~ 10-9
Ultra High
10-9 ~ 10-12
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10. Rough
Distillation
Food processing
Neon lights
Freeze drying
High
Heat treating
Deposition
Fabrication
IC Manufacturing
Thermal Insulation
Ultra high
Surface
analysis
Materials
research
Physics
research
Space
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 Mean free path
 Average distance that a molecule travels in a gas between two
successive collisions with other molecules of that gas
 It is denoted by 〈𝜆〉
 It is the product of the average speed 〈𝜈〉 and the average time
between collisions 〈𝜏〉
i.e. 𝝀 = 𝒗 ∗ 𝝉

12. Conductance
 The ability of opening to allow a given volume of gas to pass in a given time.
 It is expressed in Volume per unit Time. (Liter/sec or CC/sec)
Types of conductance
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Series conductance
•Total conductance will be equal to
the sum of individual
conductance.
•Total conductance can be
achieved by adding individual
conductance.
•C Total = C1 + C2
Parallel conductance
•Total conductance is less than the
smallest conductance of individual
pump.
•Relations become inverse in this
case.
•1/C Total = 1/C 1 + 1/C

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• Rotary Piston
• Rotary Vane
• Dry Pump
• Sorption Pump
• Booster Pump
Rough
• Oil Diffusion Pump
• Cryo Pumps
• Turbomolecular Pump
High Vacuum

14.  Type of Positive displacement pump
 To remove the atmospheric air from the system
 Mechanically compress the air and expelled out
 High speed: 1000 cubic feet per min & more
 Limited to 10mTorr
 Most widely used as roughing pump
 Main parts are hollow cylindrical pistons,
eccentric cam, discharge valve, stator, air-oil
separator
Rotor
Inlet
Exhaust
valve
Eccentric
shaft
Piston
Outlet
Oil

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1. The gas enters the piston
and drawn in region 1 through
a channel in the piston
2. The rotor continuously
rotates. The gas in region 2
is compressed.
3. When the compression is
maximum. The exhaust
valve opens, and the gas go
out.
4. The next cycle occurs
similarly

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vibration, due to balanced configuration
Rugged design fostering long life
Can handle small particulates
Cannot handle liquids
requires the use of knockout pots
The condensable vapors are not easily
handled
The discharge gas is contaminated with oil
Solvent recovery not possible, due to oil
contamination
Some designs are noisy

17.  Mechanical pump like Rotary pump
 Used for lower vacuum than rotary pump range
 Less powerful than rotary pump
 150 cubic feet per minute speed
 Used as fore pump/ Backing pump
 Consists of Rotor, sliding vane, stator, discharge valve
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18.  Also called Root Pump
 Positive displacement pump
 Used as a vacuum booster and it is designed to
remove large volume of gas
 Pressure range: ~10 - 10-5 Torr
Speeds: high speed ~4000 rpm
 The booster pump typically is found on a large
system between a high vacuum pump and a
rotary pump.
 highest pumping speeds but low compression
ratio
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 Creates a vacuum by adsorbing molecules on a very
porous material typically liquid nitrogen.
 The pressure is about till 10−7 mbar.
 The main advantages are the absence of oil or other
contaminants, low cost and vibration free operation
because there are no moving parts.
 The main disadvantages are that it cannot operate
continuously and cannot effectively
pump hydrogen, helium and neon, all gases with lower
condensation temperature than liquid nitrogen.
 The main application is as a roughing pump for
a sputter-ion pump in ultra-high vacuum experiments

20. High and Ultra high
Vacuum pumps
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21.  The oil diffusion pump is operated with an oil of
low vapor pressure.
 The high-speed jet is generated by boiling the fluid
and directing the vapor through a jet assembly
 10-1 ~ 10-7 Torr
 It consists of a chamber housing a oil vessel with a
heater, a chimney and a nozzle.
 On chamber's outer surface, cooling coils carrying
water are wound.
 These pumps are most effective when operated in
free molecular regime.
 In practical applications, it is coupled with a
backing pump.
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Diffusion pumps have no moving parts and as
a result are quite durable and reliable.
Function over pressure ranges of 10−10 to
10−2 mbar.
Driven only by convection and thus have a
very low energy efficiency.
Tendency to back stream oil into the vacuum
chamber.
Oil can contaminate surfaces inside the
chamber or upon contact with hot filaments or
Electrical discharges may result in
carbonaceous or siliceous deposits.
Due to back streaming, oil diffusion pumps are
not suitable for use with highly sensitive
analytical equipment

23.  Pumps work on the principle that gas molecules can
be given momentum in a desired direction by
repeated collision with a moving solid surface.
 A rapidly spinning fan rotor 'hits' gas molecules
from the inlet of the pump towards the exhaust in
order to create or maintain a vacuum .
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 10-2 ~ 10-8 Torr range
 It consists of alternate layers of stator and rotor discs
 The rotor rotates at a very high RPM, typically, the orders of 27000
and above.
 The blades are mounted at an optimum angle, on both stator and
rotor.
 This high-speed rotation imparts momentum to the gas particles upon
collision with the rotor discs.
 The high-speed molecules are directed towards the exit using the
stator discs.
 These two adjacent discs are often called as a stage in the TMP.
 A TMP has 6 to 7 stages depending upon the level of vacuum
required.
 These pumps are more efficient in free molecular flow regime.
 They are often backed up by mechanical pumps.
 It is high cost pump and can not build of large size.

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Clean, oil free vaporized back-streaming
Does not use any trap,
can offer an extremely clean vacuum
environment for smoking the container
does not contain any hydrocarbon.
Does not use the high vacuum valve or
thick vacuum valve. Space account is short
gasses are condensed, frozen, and
trapped, the pump requires regeneration
when its internal surfaces become
saturated
Can have vibrations
Needs mechanical pumps

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 A cryopump or a "cryogenic pump" traps gases and vapors by
condensing them on a cold surface
 Provides 10−3 to 10−9 Torr range
 The vacuuming process involves condensation of the gases onto the cold
head
 Commonly cooled by compressed helium, may also use dry ice, liquid
nitrogen ,or build in Cryocooler
 A two stage cold head unit produces temperatures of 70 K (1st stage) and
20 K (2nd stage)
 The cold head consists of a two-stage cold head cylinder (part of the
vacuum vessel) and a drive unit displacer assembly

27.  All the gases, except He, H2 and Ne are frozen at 70 K baffle and 20 K cold head.
 Gases He, H2 and Ne are adsorbed onto the charcoal provided on the underneath of the 20 K
shield.
 These pumps are self contained, hydrocarbon free and are cooled by a two stage cryocooler
Regeneration
 The surface eventually saturates with condensate .
 It will hold the trapped gases as long as it remains cold, but it will not condense fresh gases from
leaks or back streaming until it is regenerated.
 Regeneration of a cryopump is the process of evaporating the trapped gases.
 During a regeneration cycle, the cryopump is warmed to room temperature or higher, allowing
trapped gases to change from a solid state to a gaseous state through a pressure relief valve into
the atmosphere.
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28. Bourdon Gauge
Thermocouple Gauge
Pirani Gauge
Ionization Gauge
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29.  Very common and simple.
 Good for positive & negative pressure.
 Up to 0.1 Torr
 Measure relative pressure
 Not very accurate due to outer fluctuating pressure
 Components are needle, elliptical, shaped tube, levers
& gears and scale.
 Very simple mechanism
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 They can read from above atmospheric down to
about 0.1 Torr ; useful for measuring rough
vacuums.
 Uses the principle that a flattened tube tends to
straighten or regain its circular form in cross-
section when pressurized.
 The pressure changes led to change the circular
form of bourdon tube, leads the end of bourdon
tube to change its position, leads to change the
position of the pointer through the pinion
(gears).

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 Thermal conductivity guage
 Faster response.
 Detect 0.5 to 0.0001 Torr
 Tungstun wire use to sensing thermal conductivity
of gaseous molecule
 Change in temperature leads to change in
resistance
 Larger in size and more costly with complex
design.
Wheatstone bridge
Thermal
conductivity
sensor
Power
supply

32.  Work similarly to pirani gauge
 Can measure up to 0.0001 Torr
 Filament is heated by power supply
 The collision of the gas molecules and heated filament, lead to heat
loss in filament.
 The temperature of two wires in thermocouple is changed.
 Measuring the voltage changes in thermocouple through temperature
change is an indirect indication of pressure.
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33.  Also called as Hot Filament/Hot Cathode Gauge.
 Widely used for high vacuum
 Working range 10−2 to 10−10 torr
 30~50% accuracy in provided range
 Correction factor is required to calculate vacuum
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34.  Leak ?
 “The undesirable gas or liquid flow go through the hole or the crack is called the leak.”
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Vacuum
atmospheric
Chamber wall

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Outgassing
Leaks
Virtual
Real
Backstreaming
Diffusion
Permeation
-The release of traped indoor gas
-Cause : double gasket, double O-
ring, inproper welding, tiny crack
-The release of gas that was solved , traped,
frozen or absorbed in some material
-Cause: immoderate O-ring grease, outgassing
of finger oil , dirty material
Permeation leak via Elasstomer
-Cause : gas between solid material

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 Use high voltage Tesla Coil
 Only visible in glass system
 Dangerous to high voltage
 Visible sparks due to ionization of gases
 Limited sensitivity
 Measure pressure fluctuation
 Common for rough vacuum
Pressure change method
Spark coil method

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 Spark Coil Method
 Using high voltage coil to detect.
 Glow discharge at leak position
 Visible sparks due to ionization of gases

38.  Most sensitive & Common Ionization, Separation
& detection of He.
 He is used due to its many advantages over other
gases.
 Find proportion of He ion concentration present in
Spectro tube.
Why He used:
 Helium is very light
 The lightest and smallest of the inert gas molecules
( High sensitivity)
 0.0005% in the atmosphere
 Helium permits nondestructive testing
 Helium is safe.- Nontoxic, inert, not flammable, not
explosive
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Mass
spectrometer
Test
chamber
sample
Vacuum pump
for chamber
evocation
Pressure
transducer
Helium supply

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Work
Chamber
Rotary
Pump
Fore
Valve
Roughing
Valve
Main
Valve
Rotary
pump
TM pump
VentIGPG

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Flange – Using to
connect other
devices.
Valve – To control the gas
flow.
O-ring – Avoiding the
gases going out the
system.
Clamp – Holding the objects
using the compressed gas
Power supply – support
power to operate the system

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