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5-12 5708009-C
Advanced Energy
®
TO USE THE COMMON EXCITER (CEX) FEATURE (OPTIONAL)
In the common exciter (CEX) mode of operation, more than one Apex generator is
coupled into the same plasma. In this type of operation, slight differences in output
frequency or phase of the RF energy can create “beat” frequencies that may even be
visible in the plasma and which may have adverse affects on the plasma process. To
prevent unwanted beat frequencies, two Apex generators can be phase-locked together
so that they run at the same frequency and with a fixed phase relationship between
their outputs. This locking ensures repeatable RF characteristics within the plasma.
When operating in CEX mode, one Apex unit is the “master” and the other is the
“slave.” The CEX output of the master is connected to the CEX input of the slave. If
the slave unit receives a signal of the proper frequency and amplitude at its CEX input,
it automatically phase locks to that signal and tracks the master units oscillator.
More than two slave generators can be locked together to a single master unit by
“daisy chaining” the CEX outputs and inputs. That is, the CEX output of the master is
connected to the CEX input of the first slave; the CEX output of the first slave is
connected to the CEX input of the second slave, and so on. Also, any number of Apex
generators can be locked to a single system oscillator as slave units by supplying each
unit with a signal of the proper frequency and amplitude at its CEX input. (CEX input
signal requirements are indicated in “Other Electrical Specifications” on page 3-9.)
The phase relationship between the RF is fixed by the length of the cable used to
interconnect the generator’s CEX outputs and inputs. At 13.56 MHz, a single
wavelength (360º of phase rotation) is approximately 48 feet in typical 50
Ω coaxial
cable. The use of a very short CEX interconnecting cable (as supplied in the hardware
kit) between two generators results in little phase shift. Varying this length of using
commercially available phase shifters inserted in the interconnection path can provide
more control of this relationship.
FIRST TIME OPERATION
The first time you operate the Apex generator do the following.
Note: This section refers to status LEDs for verification of proper operation. If your
Apex unit does not have LEDs, refer to the Apex Virtual Front Panel or
respective I/O status indicators for verification.
1. Use the preceding installation instructions to install the generator.
2. Turn on the system circuit breakers and apply ac input to the unit.
3. When the generator received ac input, it performs self-diagnostics. If the POWER
LIMIT LED flashes, the unit has detected an error, and you will not be able to turn
RF output on. To troubleshoot an error condition, see Chapter 6,
“Troubleshooting and Customer Support.”
4. Verify that the AC ON LED is lit. If it isn’t lit, see “Troubleshooting guide” on
page 6-1.