Vladimir Zvyagintsev

The injector cryomodule for E-Linac at TRIUMF

The e-Linac project at TRIUMF, now funded, is specified to accelerate 10 mA of electrons to 50 MeV using 1.3 GHz multi-cell superconducting cavities. The linac consists of three cryomodules; an injector cryomodule with one cavity and two accelerating modules with two cavities each. The injector module is being designed and constructed in collaboration with VECC in Kolkata. The design utilizes a unique box cryomodule with a top-loading cold mass. A 4 K phase separator, 4 K / 2 K heat exchanger and JouleThomson valve are installed within each module to produce 2 K liquid. The design and status of the development are presented.

Online quality factor measurement of the SRF cavity in injector cryomodule of VECC electron LINAC

The ANURIB facility being planned at VECC will use a super-conducting electron linac (e-Linac) as photo-fission driver. The e-Linac will initially be of 30 MeV, 2 mA with an optional upgrade to 50 MeV planned in the future. An identical e-Linac is being built for the ARIEL project at TRIUMF, Canada. The 30 MeV e-linac is made using three 1.3GHz nine cell niobium cavities of Cornell-type, each cavity supplying 10 MV acceleration. The first 9-cell cavity is housed in a cryomodule called Injector Cryomodule (ICM) followed by an Accelerator Cryo-Module (ACM) comprising two 9-cell cavities. In the first phase, the ICM has been developed in collaboration with TRIUMF. The cavity operates at 1.3 GHz and 2 K. The paper highlights the online quality factor measurement of the ICM using calorimetric method.

Status of Superconducting ISAC-II and eLinac accelerators, and SRF Activities at TRIUMF

The development for superconducting accelerators has been started at TRIUMF in 2000. The main milestones and material implementations are: 2006 commissioning of Phase-I of the heavy ion superconducting accelerator ISAC-II, 2010 Phase-II, 2014 commissioning of Phase-I of the superconducting electron linear accelerator eLinac. We are using the accumulated experience and resources for farther SRF development at TRIUMF and external projects VECC, RISP, FRIB and SLAC. TRIUMF is also running fundamental studies for SRF and educational program for universities. Status of Superconducting ISAC-II and eLinac accelerators and SRF development aspects, results and plans are discussed.

520 MeV TRIUMF Cyclotron RF System: Maintenance, Tuning and Protection

1 MW CW 23 MHz RF system of the TRIUMF’s 520 MeV Cyclotron has been in operation for over 40 years. Continuous development of the RF power amplifiers, the waveguide system and the measurement and protection devices provides reliable operation and improves the performance of the RF System. In this article, operation and maintenance procedures of this RF system are analysed and recent as well as future upgrades are being analysed and discussed. In particular, we discuss the improvements of the transmission line’s VSWR monitor and its effect on the protection of the RF system against RF breakdowns and sparks. We discuss the new version of the input circuit that was installed, tested and is currently used in the final stage of RF power amplifier. We analyse various schematics and configurations of the Intermediate Power Amplifier (IPA) to be deployed in the future. INTRODUCTION TRIUMF 520 MeV Cyclotron’s high power RF system consists of three main parts – the 1.8 MW CW RF amplifier, the transmission line (TL) and the resonator [1]. The TL itself is composed of two coaxial lines with wave impedances of 50 and 30 ohm. The second part of the TL has three capacitor stations that match 50 ohm impedance of the TL’s first part with the coupling loop port of the resonator that is at TL’s terminus. Figure 1: RF System of the 520 MeV Cyclotron. TRANSMISSION LINE RESONATOR OPERATION AND SPARK PROTECTION Instability in the RF system’s operation appears when there are sparks, electrical breakdowns, multipactor discharge in the resonator and a presence of an essential screen current in the vacuum tubes. The VSWR monitor is used to protect the RF system. This monitor turns off the RF system, if the reflected power in one of the 12 channels exceeds a specified threshold value. The RF control system analyses the rate of the Dee voltage drop, classifies the events and then tries to recover the system. The follow up analysis of where sparks and electrical breakdowns took place is done using an oscilloscope. The oscilloscope operates in stand-by mode otherwise. An example of a typical signal pattern that illustrates a spark inside the resonator is presented in Fig. 2. Figure 2: Resonator RF signals following a spark, when the drive is OFF (yellow – drive amplitude, green – Dee voltage, pink – RF signal, blue – rectified voltage of the reflected signal). The rate of the Dee voltage drop allows to determine whether this spark happened inside the resonator or inside the TL and how large the spark was. The RF control system has sensors to determine the Dee voltage drop and if zero Dee voltage is detected. If either case is detected, the RF control system generates the signal to turn OFF the RF drive and to determine the time when RF system’s recovery should be attempted. However, if these sensors didn’t respond properly or responded with some delay, the standing beat wave in the TL could reach double amplitude of the original signal (Fig. 3). As a result, some parts of the TL, such as matching capacitors, the water feedthrough or the TL conductors and insulators could be damaged. To protect cyclotron’s equipment in such an event, the RF switch was built into the VSWR monitor to disconnect the RF drive from the RF amplifiers (Fig. 4). *TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada. Proceedings of RuPAC2016, St. Petersburg, Russia TUPSA034 RF power structures and systems ISBN 978-3-95450-181-6 285 C op yr ig ht

Operation and Maintenance of RF System of 520 MeV TRIUMF Cyclotron

1 MW CW 23 MHz RF system of the TRIUMF 520 MeV Cyclotron has been in operation for over 40 years. Continuous development of the RF power amplifiers, the waveguide system and of the measurement and protection devices provides reliable operation and improves the performance of the RF System. In this article, operation and maintenance procedure of this RF system are analyzed and recent as well as future upgrades are being analyzed and discussed. In particular, we discuss the improvements of the transmission line’s VSWR monitor and their effect on the protection of the RF system against RF breakdowns and sparks. We discuss the new version of input circuit that was installed, tested and is currently used in the final stage of RF power amplifier. We analyze various schematics and configurations of the Intermediate Power Amplifier (IPA) to be used in the future. The thermo-condition improvements of the Dee voltage probe’s rectifiers are described.

Balloon Variant of Single Spoke Resonator

Z. Yao, R.E. Laxdal, V. Zvyagintsev, TRIUMF, Vancouver, B.C., Canada Abstract Spoke resonators have been widely proposed and optimized for various applications. Good performance has been demonstrated by many cold tests. Accompanying the great progress, the adverse impact of strong multipacting (MP) is also noted by recent test reports, consistent with modern 3D simulations. This paper will discuss MP behaviors in the single spoke resonator. In particular a phenomenological theory is developed to highlight the details of the geometry that affect MP. The analysis leads to an optimized geometry of a single spoke resonator defined here as the ‘balloon geometry’.

TRIUMF's Injector and Accelerator Cryomodules

TRIUMF’s ARIEL project includes a 50 MeV-10mA electron linear accelerator (e-Linac) using 1.3 GHz superconducting technology. The accelerator consists of three cryomodules; an injector cryomodule with one cavity and two accelerating cryomodules, each having two cavities. One injector cryomodule and one accelerator cryomodule have been assembled and commissioned at TRIUMF, and a second injector cryomodule for VECC is being assembled in Kolkata. Both injector and accelerator cryomodules utilize a top-loaded cold mass design contained in a box-type cryomodule. The design and early test results of both cryomodules are presented.

Q‐Slope Analysis of Low‐Beta SRF Cavities

In this contribution we present Q‐slope studies performed on about 50 low beta resonators, mainly bulk Nb quarter wave cavities built and/or tested at TRIUMF. The goal of the analysis is to look for trends in the low, medium and high field Q‐slope (LFQS, MFQS, HFQS) regimes for different cavity treatments, temperature and residual resistance. We will focus on medium field Q‐slope and comparisons will then be shown between low and high beta cavities and we will draw some conclusions including a possible contribution of hydrogen to MFQS in low beta resonators.