The 3300 Series are Open-face, MCP-based, position-sensitive detector heads for particle and EUV/X-ray detection on standard or coated (e.g. CsI, KBr) MCP surface, operated in vacuum (fully UHV-compatible).  In operation, single incoming events (particles or photons) impact the MCP surface and result in an electron cascade, the gain depending on the number and type of MCP's, the bias voltage and the MCP configuration. The MCP's operate in a gain-saturated mode to ensure a relatively constant gain from event-to-event to optimize position determination.

Sensor heads are offered in circular active areas of 18 mm, 25 mm, 40 mm and 75 mm diameter, and also a 74 x 93mm rectangular active area.  Capable of spatial position resolution of 100 (standard) or 400 (high resolution) effective resolvable elements across active area.  Spatial position linearity is typically within 5% of true position (of sensor active dimension, fixed pattern).  Background count rate are typically less than 10 events per second integrated over the entire image area.  Bias voltage requirements for the microchannel plates and RAE position encoder must be provided by external 2-3 kV (3-4 kV for high resolution versions) power supply and resistive biasing network.

Options, 3300 Series

Electrically Isolated Front Rings (option 001/SE)
Electrically isolated ring options provide an additional metal ring approximately 0.125 inches (3.1 mm) in front of the standard front ring of the sensor which is at the electrical potential of the first MCP input surface. This added ring may be used for either mounting the sensor (to an aperture plate, for example, that may be at a different electrical potential than the first MCP input surface) or used for mounting an accelerating or retarding grid or other device in front of the sensor. Except in the Model 3992A (75 mm sensor) the added rings are not removable without disassembly of the sensor. They can be biased using a contact pin provided on the rear of the baseplate.

10k ohm higher speed RAE (Option 002/SH)
This option provides for a shorter-time constant, lower-resistance RAE in place of the standard RAE. All other aspects of the MCP/RAE sensor are standard. This option is offered in a 2 MCP configuration. The shorter-time constant (X10) RAE enables the use of faster shaping time of the preamplifiers, allowing he possibility of a higher achievable maximum practical counting rate of approximately 1 MHz.  For use with 2500 series.

HOT/EDR (High Output Technology/Extended Dynamic Range) Type MCP's (Option 003/SM)
In some cases, special high bias-current MCP's are used to support the higher localized counting rates encountered in some applications, often used with Option 002/SH.

6.4mm Diameter Center Hole through the sensor (Option SK)
This option provides a 6.4 mm circular hole directly through the center of the sensor, including the ceramic baseplate, RAE and MCP's. The typical purpose of this option is to enable an incident beam to travel through the sensor, on axis, in applications such as LEED (low-energy electron diffraction) and related techniques.  Due to the presence of the center hole, some residual distortion in the immediate vicinity of the center hole (extending to about 4 mm from the edge of the hole) should be expected, along with higher background count rates than with standard MCP's. Care must be exercised with this option to avoid allowing any device inserted into this hole (e.g. electron gun) from physically contacting the MCP's or RAE.

Coated MCP Options
CsI, KBr or similar coatings can be applied to input MCP surface to enhance detection efficiency for soft x-ray and vacuum uv applications. Coating and thickness can range from approximately 3000 Å to 18000 Å.