Detectors replacement in mass spectrometers

Due to the exit of some foreign companies from the Russian market, the problem of acquisition of components for domestic developers and manufacturers of mass spectrometers, in particular, detectors, has become more actual. At the same time, the problem of replacement of exhausted detectors in imported mass spectrometers already operating in the country (detector service life is 1-2 years, mass spectrometer service life is 10-15 years) has arisen.

Baspik offers TOF-detectors to developers and manufacturers of mass spectrometers, as well as services for replacement of detectors in imported mass spectrometers with domestic analogues with adaptation of the latter if necessary. 

Quadrupole and time-of-flight mass spectrometers are the most widely used.

 Dinode SEMs or channeltrons which are distributed potential SEMs are used as detectors in quadrupole mass spectrometers. The disadvantage of dinode SEMs is instability of operation at repeated exposures to the atmosphere. Channel  electron multipliers are reliable and effective detectors of positive and negative ions as well as electrons and photons. Glass surfaces can withstand multiple cycles between vacuum and atmosphere without performance degradation typical of  discrete dinode multipliers. On the other hand, the dynamic range of channel multipliers is lower due to the limitation of the output current when operating in the saturation mode. Baspik has developed a version of the serial channel multiplier SEM-6M, increasing the maximum linear mode current and thus extending its dynamic range. Parameters of  SEM-6M-1version with extended dynamic range are listed in the table below.

SEM-6М-1 parameters

ParameterNormal value
Gain at supply voltage of  Usupply ≤3000 V1×108,  min  
Dark count rate , count/s1, max
Channel strip current at Usupply =3000 V, μA70, min
Linear output current, μA10% of  channel strip current, min
Pulse height resolution at count rate of  1×103 to 5×103 count/s and Usupply corresponding to gain of 1×108 min0.8 max

Owing to its performance characteristics SEM-6М-1 can be used for measurements both in analog and counting modes.

Timeofflight mass spectrometry detects incoming ions by measuring the time it takes the ion to travel from the ion sources to the detector. Detectors for time-of-flight mass spectrometers must have fast response and must detect ions with high efficiency. Therefore, these detectors mainly use MCPs, which have high ion sensitivity and sub-nanosecond response times. Detectors for time-of-flight mass spectrometers (TOF detectors) must have an output signal without damped oscillations in addition to a short pulse width.

VTC Baspik has optimized the design of time-of-flight MCP detectors with an active area diameter of 25 mm to obtain a pulse width of less than 1 ns without damped oscillations. The performance characteristics of TOF detectors with a chevron stack of MCPs are listed in the table below.

TOF-detector parameter

Active area diameter, mm min26
Channel diameter, μm6-10
MCP qty2
Gain at MCP-assembly voltage of 2200 V, max1×107
Resistance of a single MCP, MΩ20-50
Dark count rate density, count/(s×·cm2), max2
Pulse width (FWHM), ns, max0.9

A planar detector design assembled with power supply circuit on a printed circuit board has also been created. The board on which the MCP detector is mounted consists of a detector voltage divider, components of the power supply circuit and a coaxial connector for the signal readout. The assembly of the detector on the board allows to reduce the influence of spurious inductances, and as a result, the output pulse of the MCP detector acquires a classical waveform without “ripple” with improved timing characteristics.  The compact design with 2 pins for the power supply and a coaxial connector for the signal readout is more appropriate to the application and provides easy installation and replacement of the detector when needed.