Solid State Photo-Multiplier for Charged-Particle Microscopy
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Solution Overview
Problem
Traditional electron microscopes employ bulky evacuated photo-multiplier tubes (PMTs) that are cumbersome, prone to signal loss due to long light guides, and overload at high fluxes of output radiation, limiting their compactness and versatility.
Innovation Solution
A compact Solid State Photo-Multiplier, specifically a Multi-Pixel Photon Counter, is used to detect output radiation from charged-particle microscopes, with adjustable bias to match gain to the expected flux, allowing efficient detection without saturation and enabling placement closer to the sample or within the microscope's optical column.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an evacuated photo-multiplier tube (PMT) is used to detect output radiation, then detection capability is achieved, but the detector becomes bulky and cumbersome
Solution Approach 1:
The patent changes the fundamental operating parameters of the detector by replacing the evacuated tube environment with solid-state semiconductor materials, operating at much lower voltages (tens of volts vs. kilovolts), and using different detection physics (charge carrier generation vs. photoelectron multiplication). This enables the same detection function with dramatically reduced size and weight.
Solution Approach 2:
The patent replaces the mechanical/electrical system of an evacuated tube with high-voltage dynodes and electron multiplication with a solid-state semiconductor system using electric fields and charge carrier multiplication. This substitution eliminates the need for vacuum maintenance, high-voltage insulation, and bulky structural components, achieving compact detector design.
2Adaptability or versatility
If a long light guide is used to connect the scintillator to the PMT, then spatial flexibility is achieved, but signal loss increases
Solution Approach 1:
The patent extracts and eliminates the light guide component from the detection system by placing the solid-state detector in direct contact with or very close to the scintillator. This removal of the intermediate light guide component eliminates the associated signal loss while the compact detector can still be positioned flexibly within the microscope geometry.
3Adaptability or versatility
If the PMT is placed farther from the sample due to its bulky size, then detector placement flexibility is reduced, but lens aberrations increase
Solution Approach 1:
The patent changes the physical parameters of the detector (size, weight, voltage requirements) to enable placement in positions that were previously inaccessible to bulky PMTs. The compact solid-state detector can be positioned closer to the sample and within the optical column, improving spatial resolution and reducing lens aberrations while maintaining full detection functionality.
4Reliability
If the scintillator is made less sensitive to attenuate input to the PMT, then current overload is prevented, but detection sensitivity decreases
Solution Approach 1:
The patent changes the detection mechanism from photonic radiation detection (scintillator + PMT) to direct charged particle detection (solid-state detector). This fundamental parameter change allows the detector to handle high fluxes of output radiation directly through charge carrier generation without the current overload problems of PMTs, while maintaining or improving detection sensitivity through direct interaction with the radiation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a significantly smaller, lower-voltage detector that can handle varying radiation fluxes without saturation, enabling more versatile and efficient charged-particle microscopy with improved spatial resolution and reduced lens aberrations.
Implementation Method 1
The output radiation is detected and examined using a Solid State Photo-Multiplier
Implementation Method 2
output electrons emanating from the sample move toward and strike the scintillator (which will often be maintained at an accelerating potential of the order of a few kV with respect to the sample), thus causing the production of photonic radiation
Data Source
AI summary
A method of investigating a sample using a charged-particle microscope is disclosed. By directing an imaging beam of charged particles at a sample, a resulting flux of output radiation is detected from the sample. At least a portion of the output radiation is examined using a detector, the detector comprising a Solid State Photo-Multiplier. The Solid State Photo-Multiplier is biased so that its gain is matched to the magnitude of output radiation flux.