A 500 ke V RFQ accelerator is being developed at the Texas Accelerator Center. The ion source for this machine is a magnetron type ion source with a single extraction gap. The design current is 10 mA of Hwith an energy of 30 ke V and En,eo% = 0.2 7r mm-mrad. To date, peak currents in excess of 28 mA have been extracted from this ion source indicating that the current density at the extraction aperture is 2.1 AI cm'. Preliminary emittances have been obtained 10 cm from the extraction aperture. The extracted beam is transported approximately 30 cm by a helical electrostatic quadrupole lens (HESQ). Initial low current tests of the HESQ have shown that 55 % of the focused beam lies within the RFQ acceptance.

The front IR quadrupole absorbers (TAS) and the IR neutral particle absorbers (TAN) in the high luminosity insertions of the Large Hadron Collider (LHC) each absorb approximately 1.8 TeV of forward collision products on average per pp interaction (/spl sim/235 W at design luminosity 10/sup 34/ cm/sup -2/ s/sup -1/). This secondary particle flux can be exploited to provide a useful storage ring operations tool for optimization of luminosity. A novel segmented, multi-gap, pressurized gas ionization chambers is being developed for sampling the energy deposited near the maxima of the hadronic/electromagnetic showers in these absorbers. The ionization chamber must be capable of resolving individual bunch crossings at 40 MHz. The ionization chamber is segmented into quadrants; each quadrant consists of sixty (40/spl times/40) mm/sup 2/ Cu plates 1.0 mm thick, with 0.5 mm gaps. The 0.5 mm gap width has been chosen so that the time for the ionization electrons to drift across the gap, is short enough to produce at the output of the shaping amplifier, a signal that returns to the base line is less than the 25 ns bunch spacing of the LHC. From noise considerations in the presence of a cable the stack of plates are connected electrically 10 in parallel, 6 in series to achieve an equivalent detector capacitance C/sub d//spl sim/50 pF. This type connection forms an electrode inductive L/sub e/ and electrode capacitive C/sub e/ network that must be optimized to transfer charge from the chamber to the sensing amplifier. This paper describes the design of the collection electrodes optimized for 40 MHz operation.

A description of the SSCL RFQ-DTL Matching Section instrumentation is presented with emphasis on design issues and early instrumentation commissioning results. The H{sup {minus}} beam energy through the RFQ-DTL matching section is 2.5 MeV, the beam current is 27 mA with a pulse width of 35 Its. The typical beam diameter is 3 mm. The instrumentation consists of three beam position monitors (BPM), a wire scanner, beam loss monitors (BLM), a slit and collector emittance measurement unit (EMU), a current toroid, and a Faraday cup. The instruments were designed to accommodate high current densities, have a large dynamic range with moderate bandwidths, and fit congested spaces.

Many invasive techniques for monitoring beam profile and intensity require secondary emission signals in order to make the measurement. Signal acquisition and processing can take many forms. This paper describes a bipolar integration technique which uses the Burr-Brown ACF2101 Dual Switched Integrator chip and applications for accelerator beam instrumentation.

The RFQ-DTL matching section has four variable field quadrupole magnets in a FODO lattice to match the 2.5-MeV, 27-mA, H/sup -/ beam from the RFQ to the acceptance space of the DTL, as well as to provide beam steering. In addition, there are two rf buncher cavities to provide longitudinal phase space tuning. An ensemble of beam diagnostics including input and output beam current toroids and beam position monitors, a wire scanner for beam profile measurements, a slit and collector device for beam emittance measurements, and a Faraday cup is used to quantify the matching section performance. The finalized design of the major components of the RFQ-DTL matching section is presented as well as the status of its construction.< >

A detailed description of the SSC RFQ beam instrumentation is presented. Most of the instrumentation is located in the RFQ end walls. The upstream end wall contains a segmented Faraday cup, a segmented aperture and a wire scanner. The down stream end wall contains a segmented aperture and wire scanner. Two current toroids are used to measure the transmission through the RFQ. The output of the RFQ is a low emittance, pulsed 2.5 MeV H- beam with peak current of 25 mA and maximum pulse length of 35 μs. Typical beam data are shown with the emphasis being on instrumentation performance

The integration and performance of subsystems on the Superconducting Super Collider Laboratory (SSCL) 428 MHz, 0.1% duty factor radiofrequency quadrupole accelerator is reported. Results of low- and high-power rf measurements on the RFQ cavity are compared to design specifications. Operation of the integrated RFQ vacuum, temperature and supervisory control systems are described

RF breakdown test results with copper and SiO/sub 2/-coated copper are presented. The interest was to investigate what improvement could be made in depressing the field emission and increasing the maximum field gradient by the SiO/sub 2/ coating. The results show that the breakdown started at a field level of 97-100 MV/m with the SiO/sub 2/-coated electrodes. The Kilpatrick limit at 471 MHz is 20 MV/m. This means that SiO/sub 2/ coating may provide a method for keeping the electrode surface free of damage during high field gradient operation. The SiO/sub 2/ coating can also reduce the field emission. Compared with the pure copper electrodes which were used for more than 100 h, the data show that the total normalized X-ray counts of the pure copper sample were about 20 times more than that of SiO/sub 2/-coated copper.<>

The helical electrostatic quadrupole (HESQ) lens has been proposed as a low energy beam transport system which permits intense H/sup -/ beams to be focused into a radio frequency quadrupole (RFQ) without seriously increasing the beam's emittance. A stepwise continuous HESQ lens has been constructed, and preliminary tests have shown that the structure does provide focusing. In order to understand the transport properties of this device, further detailed studies have been performed. Emittances were measured 3.5 cm from the end of the HESQ at two different voltages on the HESQ electrodes. A comparison of these experimental results with a linear model of the HESQ beam transport is made.< >

A 750 keV RFQ based accelerator is being developed at the Texas Accelerator Center. A modified magnetron ion source will produce 10--100 mA of 30 keV H{sup {minus}} beam. A 30 keV transport line that transports the beam from the ion source to the entrance of the RFQ without becoming neutralized has been designed and is under construction. The RFQ is a 86 cm long, four rod structure that operates at 470 MHz. Results of tests on the cold model are reported.