Speaker
Joseph Lu
(TRIUMF)
Description
In TRIUMF, the Eimac power tetrode vacuum tube 4CW100,000 (or 4CW150,000) is used in 3 amplifier systems. It is also used in Nordion, a medical isotope production company with collaboration with TRIUMF, in its TR-30 phase II amplifier system. In addition, the power tetrode 4CW50,000, which uses the same socket as 4CW100,000, is used in Nordion TR-30 phase I amplifier system. A test stand is needed for conditioning and testing the spare vacuum tubes so that they can be ready for these systems in case the replacement of the tubes is needed.
There was originally an amplifier served for separator, which is no longer used in the beam line. It has been de-commissioned and has been standing idolly for more than 10 years. There is also a 25KV 10 amp PEI (Power Energy Industry) high voltage supply with missing soft start (ramping up voltage) control cards standing idolly for more than 15 years. It is decided that these two units will be modified to form the test stand amplifier system.
Compared with other amplifiers, the particular modification requirements for this one are as follows:
1): To modify the construction of the output cavity centre conductor to make the removal and installation of the vacuum tubes to be easier.
2): To design an adjustable output coupling loop to reflect the different load impedance requirement for 4CW100,000 (or 4CW150,000) and 4CW 50,000.
3): To provide the filament voltage selection with 15.5 volts for 4CW100,000 (and 4CW150,000), and 12 volts for 4CW 50,000;
4): To ensure the solid state driver be able to provide enough drive power at frequencies caused by the different plate output capacitance between 4CW100,000 (or 4CW150,000) and 4CW50,000.
As for the high voltage supply, the method of soft start for our RFQ high voltage supply is used. The special feature of the method is using single phase ramping for one phase first and subsequently for another to avoid the complicated logic for ramping three phases simultaneously.
The details of the modifications will be described in the post following.
Author
Joseph Lu
(TRIUMF)
