288results about "Mutiple dynode arrangements" patented technology

The present invention provides a gamma-neutron detector based on mixtures of thermal neutron absorbers that produce heavy-particle emission following thermal capture. The detector consists of one or more thin screens embedded in transparent hydrogenous light guides, which also serve as a neutron moderator. The emitted particles interact with the scintillator screen and produce a high light output, which is collected by the light guides into a photomultiplier tube and produces a signal from which the neutrons are counted. Simultaneous gamma-ray detection is provided by replacing the light guide material with a plastic scintillator. The plastic scintillator serves as the gamma-ray detector, moderator and light guide. The neutrons and gamma-ray events are separated employing Pulse-Shape Discrimination (PSD). The detector can be used in several scanning configurations including portal, drive-through, drive-by, handheld and backpack, etc.

An improved electron multiplier bias network that limits the response of the multiplier when the multiplier is faced with very large input signals, but then permits the multiplier to recover quickly following the large input signal. In one aspect, this invention provides an electron multiplier, having a cathode that emits electrons in response to receiving a particle, wherein the particle is one of a charged particle, a neutral particle, or a photon; an ordered chain of dynodes wherein each dynode receives electrons from a preceding dynode and emits a larger number of electrons to be received by the next dynode in the chain, wherein the first dynode of the ordered chain of dynodes receives electrons emitted by the cathode; an anode that collects the electrons emitted by the last dynode of the ordered chain of dynodes; a biasing system that biases each dynode of the ordered chain of dynodes to a specific potential; a set of charge reservoirs, wherein each charge reservoir of the set of charge reservoirs is connected with one of the dynodes of the ordered chain of dynodes; and an isolating element placed between one of the dynodes and its corresponding charge reservoir, where the isolating element is configured to control the response of the electron multiplier when the multiplier receives a large input signal, so as to permit the multiplier to enter into and exit from saturation in a controlled and rapid manner.

The present invention relates to an electron multiplier including a structure which effectively prevents an electric field from leaking to the front side of an MCP due to a voltage applied to the MCP, facilitates an operation of attaching/detaching the MCP, and prevents the MCP from being damaged and so forth during the operation. The electron multiplier includes an MCP as electron multiplying means, and an outer electric field shield member for accommodating the MCP. The electric field shield cap includes a body portion surrounding at least a side face of the MCP. The electron multiplier further includes a structure by which, while the MCP is held by the outer electric field shield member and an inner electric field shield member accommodated in the outer electric field shield member, the outer electric field shield member is attached to a base of the electron multiplier so as to facilitate the operation of attaching/detaching the MCP.

A novel electron multiplier that regulates in real time the gain of downstream dynodes as the instrument receives input signals is introduced. In particular, the methods, electron multiplier structures, and coupled control circuits of the present invention enable a resultant on the fly control signal to be generated upon receiving a predetermined threshold detection signal so as to enable the voltage regulation of one or more downstream dynodes near the output of the device. Accordingly, such a novel design, as presented herein, prevents the dynodes near the output of the instrument from being exposed to deleterious current pulses that can accelerate the aging process of the dynode structures that are essential to the device.

According to the present invention, a photomultiplier tube is used with a high-speed feedback mechanism to continuously modulate the gain of the tube in response to the size of the input signal. The gain of the tube and the anode current are independently converted to ideal logarithms. These signals are then subtracted from one another to reconstruct a true logarithmic representation of the optical signal. This log-light-level signal has a higher dynamic range and faster temporal response than has previously been achieved by other methods.

Inspection systems, circuits and methods are provided to enhance defect detection by addressing saturation levels of the amplifier and analog-digital circuitry as a limiting factor of the measurement detection range of an inspection system. In accordance with one embodiment of the invention, a method for inspecting a specimen includes directing light to the specimen and detecting light scattered from the specimen. However, the step of detecting may use only one photodetector for detecting the light scattered from the specimen and for converting the light into an electrical signal. The step of detecting also includes generating a first signal and a second signal in response to the electrical signal, where the second signal differs from the first. For example, the first signal may be generated to have a higher resolution than the second signal for detecting substantially lower levels of the scattered light. In most cases, the method may use the first signal for detecting features, defects or light scattering properties of the specimen until the first signal reaches a predetermined threshold value. Once the predetermined threshold value is reached, however, the method may use the second signal for said detecting.

An amplifier circuit having an amplifier chain comprising an input port and output port with a plurality of interconnected gain stages positioned in between. The output of one interconnected gain stage provides an input to the next stage within the amplifier chain. The output port coupled to the plurality of interconnected gain stages such that the amplifier circuit output is generated from any one or more of the interconnected gain stages.

The subject invention provides for a novel photomultiplier assembly, termed the Microstructure Photomultiplier Assembly (MPA), which enables the effective conversion of light signals (received at the front of the assembly) into readily-detectable electrical signals. The MPA comprises a photocathode (which converts light into electrons and which is located in front of or on the front surface of the assembly), followed by an electron-multiplying plate, or series of plates, each made from an insulating substrate which does not emit sufficient contaminants to poison the photocathode. Each plate is coated on the front and rear faces with a conductive layer. In addition, the front face of each plate is further coated with a layer of secondary electron-emissive material which, when struck by an incoming electron, can produce secondary electrons. Each plate is perforated with channels (with non-conducting walls) and the number and geometry of these channels is designed to promote the efficient transfer and acceleration of electrons through the channel, under an applied voltage differential across the plate(s). The number of plates placed in series is determined by the desired degree of electron multiplication. At the exit of the last plate, an anode is located to collect the electrons and generate an electrical signal that can be read by conventional electronics. The anode can be a simple anode or can be a position-sensitive anode. The spacing between the photocathode, the electron-multiplying plates, and the anode is selected to promote the efficient transfer and acceleration of electrons across the assembly, as well as to promote the efficient production of secondary electrons. The photocathode, electron-multiplying plate(s) and anode are all contained within a vacuum enclosure.

A mass spectrometer detector having a coupling capacitor including an anode that is placed at a high potential of say −4.9 kV. An annular electrode is placed outside the anode. A voltage of say −5 kV is applied to the annular electrode. This reduces the potential difference between the anode and the annular electrode, mitigating the electric field. A peripheral electrode is mounted on the outer fringe of a dielectric body and stably held at a potential of say −2.5 kV, for example, by voltage-dividing resistors.

Electrons are prevented from being made incident onto an insulation part between dynodes to improve a withstand voltage. The photomultiplier tube 1 is provided with a casing having a glass substrate 40 on which a main surface 40a made with an insulating material is formed, dynodes 31 constituted with a 1^st stage to an N^th stage (N denotes an integer of 2 or more) which are arrayed so as to be spaced away sequentially from a first end side to a second end side on the main surface 40a, a photocathode 22 which is installed on the first end side so as to be spaced away from the 1^st stage dynode 31a to emit photoelectrons, and an anode part 32 which is installed on the second end side so as to be spaced away from the N^th stage dynode 31j, taking out multiplied electrons as a signal, in which a groove 44, the surface of which is made with an insulating material, is formed between two adjacent dynodes 31 on the main surface 40a of the glass substrate 40, and the 1^st stage to the N^th stage dynodes 31 are fixed on raised parts 45 adjacent to the grooves 44 on the glass substrate 40.

An electron multiplier for a system for detecting electromagnetic radiation or an ion flow is disclosed. The multiplier includes at least one active structure intended to receive a flow of incident electrons, and to emit in response a flow of electrons called secondary electrons. The active structure includes a substrate on which is positioned a thin nanodiamond layer formed from diamond particles the average size of which is less than or equal to about 100 nm.

A photomultiplier excellent in vibration resistance and improved in pulse linearity characteristic and time-response. The fourth, and sixth to ninth dynodes (Dy4, Dy6 to Dy9) have a similar shape to that of the second dynode (Dy2). The third and fifth dynodes (dy3, Dy5) are smaller than the dynode (Dy2). The first to tenth dynodes (Dy1 to Dy10) are so arranged that the dynode inner space path defined between opposed dynodes is perpendicular to the tube axis (X). The anode (A) is a mesh anode (A), and is opposed to the dynode (Dy2) with respect to the tube axis (X).

This ion detector includes an MCP and a plurality of planar dynodes respectively having a plurality of slits. The plurality of planar dynodes are stacked via spacers parallel to an electron output plane of the MCP, and the first stage planar dynode is opposed parallel to the electron output plane. In accordance with this ion detector, it is possible to obtain output signals having the linearity reaching mV order, and to shorten its pulse width to approximately 600 ps.

The invention discloses a high-collecting-efficiency micro-channel plate, a micro-channel plate type photomultiplier and a preparation method thereof. The photomultiplier has a structure which can realize high gain, high collecting efficiency, good single photoelectron spectrum, and collecting efficiency uniformity. The photomultiplier disclosed by the invention comprises a glass ball shell, an electronic focusing barrel, a photocathode and a micro-channel plate electron multiplication system. A metal electrode surface of a first micro-channel plate in an electron incident direction of an electron multiplier of the micro-channel plate type photomultiplier disclosed by the invention and the inner wall surface of a channel are both covered with a thin film with a high secondary electron emission coefficient, so that effective multiplication of electrons can be realized and the high collecting efficiency and the collecting efficiency uniformity of the photomultiplier can be improved.