Vacuum Feedthrough Research Articles

Instrumentation for Negative Ion Detection

The instrumentation and practical circuitry required for the detection of negative ions exiting the mass analysis section of a mass spectrometer is examined. The potentials needed to bias the electron multiplier when detecting negative ions from a low ion-energy mass spectrometer, e.g., a quadrupole, are contrasted with the biasing requirements of a mass spectrometer having high ion-energies, e.g., a magnetic sector. Methods of decoupling the biasing high voltage on the signal lead of the multiplier in pulse counting measurements are discussed in detail so that normal, ground referenced input, pulse preamplifiers may be used. Easily understood, practical rules for determining the values of circuit components are given together with a simplified theory of transferring pulse signals from multiplier collector to pulse preamplifier. The changes in circuitry needed when attempting to detect ions by current measurement methods from an electron multiplier area detailed. The effects of leakage currents into athe input of the current preamplifier and their avoidance bay using triaxial shielding on vacuum feed-throughs are explained. The article suggests possible methods of decoupling the high voltage referenced input and the ground referenced output of a current measuring preamplifier.

Instrumentation for negative ion detection.

The instrumentation and practical circuitry required for the detection of negative ions exiting the mass analysis section of a mass spectrometer is examined. The potentials needed to bias the electron multiplier when detecting negative ions from a low ion-energy mass spectrometer, e.g., a quadrupole, are contrasted with the biasing requirements of a mass spectrometer having high ion-energies, e.g., a magnetic sector. Methods of decoupling the biasing high voltage on the signal lead of the multiplier in pulse counting measurements are discussed in detail so that normal, ground referenced input, pulse preamplifiers may be used. Easily understood, practical rules for determining the values of circuit components are given together with a simplified theory of transferring pulse signals from multiplier collector to pulse preamplifier. The changes in circuitry needed when attempting to detect ions by current measurement methods from an electron multiplier area detailed. The effects of leakage currents into athe input of the current preamplifier and their avoidance bay using triaxial shielding on vacuum feed-throughs are explained. The article suggests possible methods of decoupling the high voltage referenced input and the ground referenced output of a current measuring preamplifier.

Cryogenic performance of coaxial, multi-pin and coaxial-multi-pin complex bakable feedthroughs

Five BNC-type coaxial (BNC-receptacle, BNC-receptacle with floating shield, BNC-receptacle with floating and reverse sleeve, BNC-JJ, and BNC-JJ with floating shield), four N-type coaxial (N-receptacle, N-receptacle with floating shield, N-JJ, and N-JJ with floating shield), 22 pin, and 14 pin-BNC complex vacuum feedthroughs have been constructed. They are bakable (600 K) and can be used below helium lambda temperature (2.17 K), and remain leak-tight (⩽ 10 −18 kNms −1). Moreover, there is no leak at a pressure difference of 1.5 × 10 3 kNm −2 of helium at room temperature. BNC-JJ has a VSWR ⩽ 1.35 from dc to 4.0 GHz. N-JJ has a VSWR ⩽ 1.25 from dc to 6.5 GHz. 22 pin and 14 pin-BNC xcomplex vacuum feedthroughs can be quickly connected by Burndy connectors.

An Inexpensive Positron Converter of High Reliability and High Yield

A new positron converter of the simplest construction is described, consisting of a multiple fixed tungsten target and a very small helical positron lens, both inside a small vacuum chamber. By utilizing the good vacuum insulating properties the lens may be pulsed with 6000 A at an operating voltage of 10 kV without insulating material, except for the vacuum feed throughs, for which the extremely radiation-resistant aluminiumoxide ceramic is used. The lens construction out of a copper pipe allows direct water cooling and gives sufficient mechanical strength without further reinforcement. The system has been in operation for 3 years and gives a positron conversion ratio I+/I- of 0.8 % as a routine value for an e--energy of 300 MeV, where the positron energy spread is within ± 1.5 MeV. Compared to a dc-lens saving factors of about 500 in weight, 50 in power consumption and 100 in cost have been achieved.

Improvement of a beam position monitor for Δr feedback on RF system

When the beam intensity of the 12 GeV proton synchrotron is increased, oscillations occur in the radial direction of the beam, and the beam loss increases at the phase transition. The beam loss at the transition point was due to the ΔR feedback system oi RF acceleration. The ordinary electrostatic pickup <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1)</sup> used for RF feedback system was replaced with a new large size pickup <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2)</sup> . Improvements were made in the following respects: 1. large size to obtain high signal to noise ratio, 2. no side walls to eliminate the noise due to beam hitting, 3. smooth ground for the shield electrode, 4. minimization of the distance between the electrode and vacuum feedthrough and the insertion of an oscillation damping resistor between them, 5. calibration wires were installed between the sensing electrode and the shield electrode. Electrode signals were processed by an average type rectifier and normalizer. The position signal was fed to an RF system through an analogue isolator. This paper deals with the modifications in the beam position feedback of the RF system.

3791. Inexpensive rotary/push-pull vacuum feedthrough. (USA): M A Hutchinson,J Vac Sci Technol, 14 (6), 1977, 1320

3791. Inexpensive rotary/push-pull vacuum feedthrough. (USA): M A Hutchinson,J Vac Sci Technol, 14 (6), 1977, 1320

2. Ultra-high vacuum and cryogenic feedthrough with 48 pins

2. Ultra-high vacuum and cryogenic feedthrough with 48 pins

2. N—JJ coaxial, bakeable and cryogenic vacuum feedthrough with an isolated shield useful from de to 6.5 GHz

2. N—JJ coaxial, bakeable and cryogenic vacuum feedthrough with an isolated shield useful from de to 6.5 GHz

3826. BNC-JJ coaxial floating shield bakable and coolable vacuum feedthrough??? useful from dc to 4 GHz. (USA): H Ishimaru,Rev scient Instrum,49 (4), 1978, 545–546

3826. BNC-JJ coaxial floating shield bakable and coolable vacuum feedthrough??? useful from dc to 4 GHz. (USA): H Ishimaru,Rev scient Instrum,49 (4), 1978, 545–546

BNC–JJ coaxial floating shield bakable and coolable vacuum feedthrough useful from dc to 4 GHz

A floating (10(11) Omega), bakable (300 degrees C), coolable (liquid helium temperature) BNC-JJ-type coaxial vacuum feedthrough is described. It has a VSWR < or =1.22 from dc to 1.3 GHz and < or =1.35 from 2.0 to 4.0 GHz.

Bakeable vacuum feedthrough with 22 pins

Bakeable vacuum feedthrough with 22 pins

A compact small aperture straight-through vacuum valve

We report the design of an inexpensive and flexible fibre-optic bundle high vacuum feed-through that can be constructed from easily available Swagelok Ultra-Torr™ stock parts. The fibre bundle extends through the vacuum envelope and thus does not suffer the transmission losses encountered when using face-to-face couplings. The flexibility of construction allows the fitting to be customised to suit all flange designs such as CF, KF or custom mountings. The use of Viton™ o-rings allows modest baking (max 200 °C) for high vacuum applications and fibre bundles can be easily repositioned, removed or replaced.

A simple, fully screened, high-voltage vacuum feedthrough. (GB)

A simple, fully screened, high-voltage vacuum feedthrough. (GB)

Bakeable vacuum feedthrough with 14 pin and BNC coaxial combination for nude B-A gauge

Bakeable vacuum feedthrough with 14 pin and BNC coaxial combination for nude B-A gauge

A simple, fully screened, high-voltage vacuum feedthrough

A high-vacuum feedthrough is described which is small and simple to construct and incorporates rigorous screening against noise pick-up. Rotary and linear displacements can be transmitted across the vacuum interface by the feedthrough.

Inexpensive rotary/push–pull vacuum feedthrough

Inexpensive rotary/push–pull vacuum feedthrough

Counterstreaming Electron Beam Profile and Position Monitor

Individual profiles and positions of two counterstreaming 10 MeV electron beams have been measured using the strongly forward directed bremsstrahlung radiation produced when a small fraction of the beam impinges on a tantalum foil. The 0.02 mm wide foil is driven through the electron beams by an external motor connected to the foil by a linear vacuum feedthrough. Bremsstrahlung radiation is detected by a series of ordinary semiconductor diodes spaced around the circumference of the beam vacuum pipe in two planes. The planes are on opposite sides of the foil and are equidistant and parallel to the plane of motion of the foil. The diodes produce output currents proportional to the bremsstrahlung radiation intensity and require no biasing voltages. Design and operational features of the beam monitor for electron beams up to 100 MeV are described. Measurements on counterstreaming 10 MeV pulsed electron beams are presented. Spatial resolutions of 0.3 mm are easily discernable.

Coaxial cables as feedthroughs for high-vacuum and low-temperature applications

The adaptation of small, commercially available coaxial cable for use as a vacuum feedthrough to a low-temperature apparatus is described.

Bakeable vacuum feedthrough with 22 pins

A bakeable (300°C), small size (outer diameter, 28 mm), quick contact (Burndy connector G6F18-22 SNE, G18-22S and RC 20M-13D28), gold plated and weldable 22-pins vacuum feedthrough is described.

2471. Insulated bakeable BNC type coaxial vacuum feedthrough

2471. Insulated bakeable BNC type coaxial vacuum feedthrough