System Manual
Oxford Instruments Plasma Technology
Plasmalab and Ionfab
Measurement of RF & Microwave Emissions
Printed: 5-Jun-09, 9:58
Page 3 of 4
Issue 2: December 01
3.
Acceptable exposure standards
Readings must be equal to or less than the levels shown in Table 1 at all points. Exceptions will only
be permitted in certain special circumstances. These exceptions will be clearly documented in the
system instructions. In all other situations, these standards must be strictly met.
Table 1 - Maximum permitted field strengths
4.
System design
RF and Microwave components such as RF ion sources may be purchased from Oxford Instruments
Plasma Technology and fitted to the customer's system. Such an installation requires a system
designed to prevent leakage of RF and Microwave emissions, and requires careful testing by the
installer before use.
It is not possible to give a full list of necessary safety precautions, and advice should be sought from
a competent authority. However, some of the points to be considered are as follows:
(a)
The system and all of its assemblies should be very well grounded (earthed), using low
impedance straps, and ensuring impedances between power supplies and the chamber of
0.1 Ohms at 25 A.
(b)
Viewports should be shielded with fine conducting mesh to prevent the transmission of RF
and Microwave energy, and should be filtered to prevent the transmission of UV light.
(c)
Doors and flanges should provide metal-to-metal contact. In case of doubt, and in the case
of access doors, the use of copper beryllium finger strips or wire mesh over elastomer core
(e.g. Zemrex products from Warth International
should be considered. Small flanges in the
vacuum system should be joined with metal clamps, not plastic.
(d)
All types of electrical feedthrough and vacuum gauges, together with cables leaving them,
may need shielding.
(e)
Interlocks will need to be wired into the system to ensure safe operation. These will include
interlocks with the system access door, the customer's water supply to the RF product, and
the system vacuum. The product purchased from Oxford Instruments Plasma Technology will
also have interlock switches. These interlocks must all force the disconnection of power from
the RF, Microwave and HV power supplies if they are opened. See the product manual for
more details.
3
Warth International Ltd, Charlswood Road, East Grinstead, Sussex, England, RH19 2HH.
Frequency
Electric Field (E)
Magnetic field (H)
V/m
mW/cm
2
A/m mW/cm
2
0.1 to 1 MHz
614
16.3/f
1.7 to 2.1 MHz
614
16.3/f
13.56 MHz and 27.12 MHz
1842/f
900/f
2
16.3/f
10000/f
2
2.45 GHz
f/300
f/300
Note – f is the frequency in MHz
Reference: ANSI/IEEE C95.1 maximum permissible exposure for controlled
environments.
Summary of Contents for OpAL
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