Kore Components:
Ion detection assemblies
20kV bipolar post-acceleration MCP.
20kV bipolar post-acceleration detector
A time-of-flight mass analyser has no inherent mass limitation, but the detection efficiency of a micro channel-plate detector assembly decreases with mass, because, at a given ion energy, heavier ions have a lower conversion efficiency to electrons. The relatively modest ion acceleration used in the standard detector assembly limits the mass range to around 5,000 amu for inorganic cluster-ions and less for large organic ions.
It is possible to increase the sensitivity for high-mass ions by using post-acceleration to increase the energy of the initial impact between ion and detector. One way to do this is to float the detector to a high voltage with respect to ground. There is then the question of managing the high electric fields created so as to avoid arcs/discharges and finding a way to couple the ion signal to a ground based detection system.
Features
The first photograph shows the in-vacuo assembly which mounts a 25mm active area dual microchannelplate assembly from a high voltage insulator so it can be floated at up to 20kV.
The second photo shows the grounded external safety cover. Inside are bias chains, capacitative coupling/decoupling and a fast preamplifier for driving a 50 Ohm signal cable.
To keep costs low, a single high-voltage supply is provided. A resistor chain inside the safety cover divides this voltage to provide post-acceleration and excitation for the multiplying detector. As the detector ages with time the excitation will need to be increased, which will tend to increase the post-acceleration also. Eventually, a simple resistor change is required to keep the highest voltage at no more than 20kV.
To switch the polarity of ions detected, the high voltage power supply is reversed and two leads on the detector are simply swapped.
Specifications
Type of Detector:
- 25mm Active area, Dual MCP (chevron type) with housing and electrical connections.
- Post-acceleration voltage 20kV (variable)
High voltage Power supplies:
- 20kV high voltage power supply with suitable current rating for post-acceleration
- Power supply for MCP through a resistive chain network
- Input : 230 VAC ±5%, 50 Hz, Single phase (110V, 60Hz also possible)
Vacuum part:
- Ultrahigh vacuum compatible 10-8 mbar.
- Electrostatic shielding provided to avoid any disturbance in the flight path of the ions due to high voltages.
- Suitable electrical feedthroughs with rating > 20kV for providing electrical voltages
Detector Mounting:
- Completely shielded and grounded with suitable openings for pumping
- Vertically mounted on a CF 100 (152 mm OD) Conflat flange
- Height of the detector from the flange will be adjusted as per the conditions of the system
Pre-amplifier:
- Local pre-amplifier for maximum count rates and fast rise and fall times (<2ns)
- Low voltage, low noise, power supplies to operate the pre-amplifier included
- Dark noise with all components at operational voltages and with pre-amplifier will be < 10 cps
PRICING AND ORDERING
Kore Technology is a centre of excellence in time-of-flight mass spectrometer technology and has a very strong R&D capability in terms of its personnel, all of whom have been heavily involved in a variety of analytical instrumentation development programmes.
If you have any questions please feel free to contact us via our online form or telephone us for more information, we offer a wide range of products and services to suit your requirements.
If you wish to purchase our products, please contact Kore sales at sales@kore.co.uk, or call +44 (0)1353 653030.
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