This article describes the new primary proton beamline 1U at TRIUMF. The purpose of this beamline is to produce ultracold neutrons (UCN) for fundamental-physics experiments. It delivers up to 40 µA of 480 MeV protons from the TRIUMF cyclotron to a tungsten spallation target and uses a fast kicker to share the beam between the Center for Molecular and Materials Science and UCN. The beamline has been successfully commissioned and operated with a beam current up to 10 µA, facilitating first large-scale UCN production in Canada.

Abstract.A LabVIEW program running on a Sun SPARCstation 5 controls a Tektronix TDS820 6 GHz sampling oscilloscope via an Ethernet to GPIB adapter. A PC based X Window terminal continuously displays the trace, refreshed at 7 Hz. Functions such as gain, time base and application specific controls are selected by menus, buttons and dialog boxes. We have used the system to observe signals from fast (>1 GHz) Faraday cups (FFC) in the radio frequency quadrupole (RFQ) section of our Radioactive Beam Facility (ISAC). The setup utilizes the accelerator control display terminals while allowing the oscilloscope to be closer to the FFC's. ISAC uses the RFQ to accelerate singly charged ions to 0.15 MeV/u where they are stripped prior to acceleration in a drift tube linac (DTL). The time structure of the beam at the RFQ entrance was measured on a FFC placed 4 m downstream of the RFQ pre-buncher. Additional 50 Ω coaxial cone FFC's were installed downstream of the RFQ near the RFQ exit, just ahead of the stripping foil and at a double focus following the charge selection slit. The last FFC shows the increase in the mean drift time and broadening associated with the increase in energy loss and straggling caused by foil thickening under ion bombardment. Although the phase broadening cannot be corrected, the increase in the mean drift time can be corrected by changing the bias voltage on the stripper foil and thus keeping the ions in phase with the rebuncher rf.

A fast-switching, high-repetition-rate magnet and power supply have been developed for and operated at TRIUMF, to deliver a proton beam to the new ultracold neutron (UCN) facility. The facility possesses unique operational requirements: a time-averaged beam current of 40 µA with the ability to switch the beam on or off for several minutes. These requirements are in conflict with the typical operation mode of the TRIUMF cyclotron which delivers nearly continuous beam to multiple users. To enable the creation of the UCN facility, a beam-sharing arrangement with another facility was made. The beam sharing is accomplished by the fast-switching (kicker) magnet which is ramped in 50 µs to a current of 193 A, held there for approximately 1 ms, then ramped down in the same short period of time. This achieves a 12 mrad deflection which is sufficient to switch the proton beam between the two facilities. The kicker magnet relies on a high-current, lowinductance coil connected to a fast-switching power supply that is based on insulated-gate bipolar transistors (IGBTs). The design and performance of the kicker magnet system and initial beam delivery results are reported.

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