Showing papers by "Brian Chase published in 2007"

ILC Reference Design Report Volume 3 - Accelerator

Abstract: The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency (SCRF) accelerating cavities. The ILC has a total footprint of about 31 km and is designed for a peak luminosity of 2x10^34 cm^-2 s^-1. The complex includes a polarized electron source, an undulator-based positron source, two 6.7 km circumference damping rings, two-stage bunch compressors, two 11 km long main linacs and a 4.5 km long beam delivery system. This report is Volume III (Accelerator) of the four volume Reference Design Report, which describes the design and cost of the ILC.

Design of the ILC Crab Cavity System

Abstract: The International Linear Collider (ILC) has a 14 mrad crossing angle in order to aid extraction of spent bunches. As a result of the bunch shape at the interaction point, this crossing angle at the collision causes a large luminosity loss which can be recovered by rotating the bunches prior to collision using a crab cavity. The ILC baseline crab cavity is a 9-cell superconducting dipole cavity operating at a frequency of 3.9 GHz. In this paper the design of the ILC crab cavity and its phase control system, as selected for the RDR 1 in February 2007 is described in fuller detail.

Multi-batch slip stacking in the main injector at fermilab

Abstract: The Main Injector (MI) at Fermilab is planning to use multi-batch slip stacking scheme in order to increase the proton intensity at the NuMI target by about a factor of 1.5.[1] [2] By using multi-batch slip stacking, a total of 11 Booster batches are merged into 6, 5 double ones and one single. We have successfully demonstrated the multi- batch slip stacking in MI and accelerated a record intensity of 4.6E13 particle per cycle to 120 GeV. The technical issues and beam loss mechanisms for multi- batch slip stacking scheme are discussed.

Technique for monitoring fast tuner piezoactuator preload forces for superconducting RF cavities

Abstract: The technology for mechanically compensating Lorentz Force detuning in superconducting RF cavities has already been developed at DESY. One technique is based on commercial piezoelectric actuators and was successfully demonstrated on TESLA cavities [1]. Piezo actuators for fast tuners can operate in a frequency range up to several kHz; however, it is very important to maintain a constant static force (preload) on the piezo actuator in the range of 10 to 50% of its specified blocking force. Determining the preload force during cool-down, warm-up, or re-tuning of the cavity is difficult without instrumentation, and exceeding the specified range can permanently damage the piezo stack. A technique based on strain gauge technology for superconducting magnets has been applied to fast tuners for monitoring the preload on the piezoelectric assembly. The design and testing of piezo actuator preload sensor technology is discussed. Results from measurements of preload sensors installed on the tuner of the Capture Cavity II (CCII )[2] tested at FNAL are presented. These results include measurements during cool-down, warm- up, and cavity tuning along with dynamic Lorentz force compensation.

Commissioning and early operating experience with the Fermilab horizontal test facility

Abstract: Fermilab has constructed a facility for testing dressed superconducting radiofrequency (RF) cavities at 1.8 K with high-power pulsed RF. This test stand was designed to test both 9-cell 1.3 GHz TESLA-style cavities and 9-cell 3.9 GHz cavities being built by Fermilab for DESY's TTF-FLASH facility. An overview of the test stand and a description of its initial commissioning is described here.

A 96 channel receiver for the ILCTA LLRF system at fermilab

Abstract: The present configuration of an ILC main LINAC RF station has 26 nine cell cavities driven from one klystron. With the addition of waveguide power coupler monitors, 96 RF signals will be down-converted and processed. A down-converter chassis is being developed that contains 12 eight-channel analog modules and a single up- converter module. This chassis will first be deployed for testing a cryomodule composed of eight cavities located at New Muon Laboratory (NML) - Fermilab. Critical parts of the design for LLRF applications are identified and a detailed description of the circuit with various characteristic measurements is presented. The board is composed of an input band-pass filter centered at 1.3 GHz, followed by a mixer, which down-converts the cavity probe signal to a proposed 13 MHz intermediate frequency. Cables with 8 channels per connector and good isolation between channels are being used to interconnect each down-converter module with a digital board. As mixers, amplifiers and power splitters are the most sensitive parts for noise, nonlinearities and crosstalk issues, special attention is given to these parts in the design of the LO port multiplication and distribution.

Multichannel vector field control module for LLRF control of superconducting cavities

Abstract: The field control of multiple superconducting RF cavities with a single Klystron, such as the proposed RF scheme for the ILC, requires high density (number of RF channels) signal processing hardware so that vector control may be implemented with minimum group delay. The MFC (Multichannel Field Control) module is a 33- channel, FPGA based down-conversion and signal processing board in a single VXI slot, with 4 channels of high speed DAC outputs. A 32-bit, 400MHz floating point DSP provides additional computational and control capability for calibration and implementation of more complex control algorithms. Multiple high speed serial transceivers on the front panel and the backplane bus allow a flexible architecture for inter-module real time data exchanges. An interface CPLD supports the VXI bus protocol for communication to a SlotO CPU, with Ethernet connections for remote in system programming of the FPGA and DSP as well as data acquisition.

Capture cavity II results at FNAL

Abstract: As part of the research and development towards the International Linear Collider (ILC), several test facilities have been developed at Fermilab This paper presents the latest Low Level RF (LLRF) results obtained with Capture Cavity II (CCII) at the ILC Test Accelerator (ILCTA) test facility The main focus will be on controls and RF operations using the SIMCON based LLRF system developed in DESY Details about hardware upgrades and future work will be discussed

Residual phase noise measurements of the input section in a receiver

Abstract: If not designed properly, the input section of an analog down-converter can introduce phase noise that can prevail over other noise sources in the system. In the paper we present residual phase noise measurements of a simplified input section of a classical receiver that is composed of various commercially available mixers and driven by an LO amplifier.

The ILC global control system

Abstract: The scale and performance parameters of the ILC require new thinking in regards to control system design. This design work has begun quite early in comparison to most accelerator projects, with the goal of uniquely high overall accelerator availability. Among the design challenges are high control system availability, precision timing and rf phase reference distribution, standardizing of interfaces, operability, and maintainability. We present the current state of the design and take a prospective look at ongoing research and development projects.

Capture cavity II results at FNAL

Abstract: As part of the research and development towards the International Linear Collider (ILC), several test facilities have been developed at Fermilab. This paper presents the latest Low Level RF (LLRF) results obtained with Capture Cavity II (CCII) at the ILC Test Accelerator (ILCTA) test facility. The main focus will be on controls and RF operations using the SIMCON based LLRF system developed in DESY. Details about hardware upgrades and future work will be discussed.

Controls, LLRF and instrumentation systems for ILC test facilities at Fermilab

Abstract: The major controls and instrumentation systems for the ILC test areas and the NML test accelerator at Fermilab are discussed. The test areas include 3 separate areas for vertical superconducting RF cavity testing, horizontal cavity testing,and NML RF and beam test area. A common control infrastructure for the test areas including a controls framework,electronic logbook and cavity database will be provided, while supporting components supplied by collaborators with diverse areas of expertise (EPICS,DOOCS,LabVIEW,and Matlab). The discussions on the instrumentation systems are focused on overview and requirements.

Longitudinal momentum mining of antiprotons at the fermilab recycler: past, present and future

Abstract: The technique of longitudinal momentum mining (LMM) in the Fermilab Recycler was adopted in early 2005 to extract thirty-six equal intensity and equal 6D- emittance antiproton bunches for proton-antiproton collider operation in the Tevatron. Since that time, several improvements have been made in the Recycler and the mining technique to handle higher intensity beams. Consequently, the Recycler has become a key contributor to the increased luminosity performance observed during Tevatron Run lib. In this paper, we present an overview of the improvements and the current status of the momentum mining technique.

Uniform longitudinal beam profiles in the Fermilab Recycler using adaptive RF correction

Abstract: The Fermilab recycler ring is a permanent magnet based 8 GeV anti-proton storage ring. A wideband RF system, driven with ARB's (ARBitrary waveform generators), allows the system to produce programmable barrier waveforms. Beam current profile distortion was observed, its origin verified both experimentally and theoretically, and an FPGA-based correction system was designed, tested and implemented to level the bunch profile.

ANALYSIS OF MAIN PARAMETERS IN THE RECEIVER Broad-band Noise Figure

Abstract: The present configuration of an ILC main LINAC RF station has 26 nine cell cavities driven from one klystron. With the addition of waveguide power coupler monitors, 96 RF signals will be down-converted and processed. A down-converter chassis is being developed that contains 12 eight channel analog modules and a single upconverter module. This chassis will first be deployed for testing a cryomodule composed of eight cavities located at New Muon Laboratory (NML) - Fermilab. Critical parts of the design for LLRF applications are identified and a detailed description of the circuit with various characteristic measurements is presented. The board is composed of an input band-pass filter centered at 1.3GHz, followed by a mixer, which down-converts the cavity probe signal to a proposed 13 MHz intermediate frequency. Cables with 8 channels per connector and good isolation between channels are being used to interconnect each down-converter module with a digital board. As mixers, amplifiers and power splitters are the most sensitive parts for noise, nonlinearities and crosstalk issues, special attention is given to these parts in the design of the LO port multiplication and distribution.