IPAC2011 - List of Authors (Sirtl, J.)

Paper	Title	Page
MOPC129	Compact Solid State RF-Modules for Direct Drive RF-linacs	382
	R. Irsigler, M. Back, R. Baumgartner, O. Heid, T.J.S. Hughes, M. Kaspar, T. Kluge, J. Sirtl, K. Weidner, M. Zerb Siemens AG, München, Germany
	We present a modular RF power source concept based on solid state RF-modules with novel SiC transistors. The concept offers lower cost, better reliability and reduced maintenance compared to traditional RF-source technology. No circulators are required, which makes the RF-module very compact and reliable. The SiC power transistor has a very low input capacitance and was optimized for low gate resistance to enable fast switching in the VHF range. It delivers a maximum pulsed drain saturation current of 65 A. The transistor provides at 350 V supply voltage and 150 MHz an output power of 5,6 kW at a gain of 15,8 dB. It is essential to avoid high parasitic source inductances at RF and good thermal conductivity is required for operation at high duty cycle. We have built very compact 75 x 90 mm ceramic amplifier modules using a planar interconnect technology (SIPLIT) to connect the bare die transistors to the DCB substrate. The modules have a fully symmetric push-pull topology (circlotron) with four transistors in parallel in each leg. The RF-modules delivered at 150 MHz an impressive RF output power in the range of 40 kW. Further tests at 324 MHz are planned and will be presented.

MOPC152	Digital Control System for Solid State Direct Drive™ RF-Linacs	436
	J. Sirtl, M. Back, T. Kluge Siemens AG, Erlangen, Germany H. Schröder ASTRUM IT GmbH, Erlangen, Germany
	The Solid State Direct Drive™ concept for RF linacs has previously been introduced. Due to the different methodology (i.e. solid state based rather than electron tube based) as compared with conventional RF sources a new control system is required to deliver the required LLRF. To support this new technology a fully digital control system for this new concept has been developed. Progresses in Digital – Analogue Converter technology and FPGA technology allows us to create a digital System which works in the 150 Mhz baseband. The complete functionality was implemented in a Virtex 6 FPGA. Dispensing with the PLL allows an excellent jitter-behaviour. For this job, we use three 12 bit ADCs with a Sampling Rate of 1 GS/s and two 16 bit DACs (1 GS/s). The amplitude of the RF source is controlled by dividing the RF modules mounted on the power combiner* into two groups and controlling the relative phase of each group (in effect mimicking an “out-phasing” amplifier). This allows the modules to be operated at their optimum working point and allows a linear amplitude behaviour. * O. Heid, T. Hughes, Proc. of IPAC10, THPD002, p. 4278, Kyoto, Japan (2010). ** O. Heid, T. Hughes, Proc. of LINAC10, THPD068, Tsukuba, Japan.

Paper

Title

Page

Compact Solid State RF-Modules for Direct Drive RF-linacs

382

R. Irsigler, M. Back, R. Baumgartner, O. Heid, T.J.S. Hughes, M. Kaspar, T. Kluge, J. Sirtl, K. Weidner, M. Zerb
Siemens AG, München, Germany

We present a modular RF power source concept based on solid state RF-modules with novel SiC transistors. The concept offers lower cost, better reliability and reduced maintenance compared to traditional RF-source technology. No circulators are required, which makes the RF-module very compact and reliable. The SiC power transistor has a very low input capacitance and was optimized for low gate resistance to enable fast switching in the VHF range. It delivers a maximum pulsed drain saturation current of 65 A. The transistor provides at 350 V supply voltage and 150 MHz an output power of 5,6 kW at a gain of 15,8 dB. It is essential to avoid high parasitic source inductances at RF and good thermal conductivity is required for operation at high duty cycle. We have built very compact 75 x 90 mm ceramic amplifier modules using a planar interconnect technology (SIPLIT) to connect the bare die transistors to the DCB substrate. The modules have a fully symmetric push-pull topology (circlotron) with four transistors in parallel in each leg. The RF-modules delivered at 150 MHz an impressive RF output power in the range of 40 kW. Further tests at 324 MHz are planned and will be presented.

MOPC152

Digital Control System for Solid State Direct Drive™ RF-Linacs

436

J. Sirtl, M. Back, T. Kluge
Siemens AG, Erlangen, Germany
H. Schröder
ASTRUM IT GmbH, Erlangen, Germany

The Solid State Direct Drive™ concept for RF linacs has previously been introduced*. Due to the different methodology (i.e. solid state based rather than electron tube based) as compared with conventional RF sources a new control system is required to deliver the required LLRF. To support this new technology a fully digital control system for this new concept has been developed. Progresses in Digital – Analogue Converter technology and FPGA technology allows us to create a digital System which works in the 150 Mhz baseband. The complete functionality was implemented in a Virtex 6 FPGA. Dispensing with the PLL allows an excellent jitter-behaviour. For this job, we use three 12 bit ADCs with a Sampling Rate of 1 GS/s and two 16 bit DACs (1 GS/s). The amplitude of the RF source is controlled by dividing the RF modules mounted on the power combiner** into two groups and controlling the relative phase of each group (in effect mimicking an “out-phasing” amplifier). This allows the modules to be operated at their optimum working point and allows a linear amplitude behaviour.
* O. Heid, T. Hughes, Proc. of IPAC10, THPD002, p. 4278, Kyoto, Japan (2010).
** O. Heid, T. Hughes, Proc. of LINAC10, THPD068, Tsukuba, Japan.