The (e,2e) spectrometer vacuum chamber (figure 1) is manufactured from 304 grade stainless steel, the construction being carried out by Vacuum Generators using a design of Jones, Read and Cvejanovic, full details of which may be found in T. 3mm thick mu-metal magnetic shielding is placed both internally and externally to decrease extraneous external magnetic fields to less than 5mG at the interaction region.
All inputs and outputs to the spectrometer pass through the vacuum chamber via feedthroughs on the top flange.
The top flange of the vacuum system is a 25mm stainless steel flange with 11 conflat CF70 flanges arranged around a central 200mm flange designed for locating a hydrogen source. Two flanges are used for the high voltage channeltron and photomultiplier tube inputs and pulse outputs. Three rotary motion feedthroughs allow the analysers and electron gun angles to be changed externally via stepper motors for both analysers and for the electron gun. The ionisation gauge is placed at right angles to the main flange to prevent light from the thoriated iridium filament entering the vacuum system, which would increase noise on the photomultiplier tube. The ionisation gauge feedthrough is sooted, and a loose cover is placed over the entrance in the chamber flange to prevent stray light from the ion gauge entering the vacuum system.
The target gas enters the system via a CF70 flange which has two 6mm stainless steel tubes welded into the flange.
The other gas feed is connected to a hypodermic needle set at 90A° to the incident beam for measurements in other geometries. The gas jet which is not currently used in the interaction region can be used to non-locally fill the chamber with gas for background counting measurements.
The final CF70 flange is used when the photomultiplier tube is cooled, usually during baking of the system following exposure to atmosphere.
The tube is cooled by passing vapour from a liquid nitrogen source through expansion coils wrapped around the photomultiplier tube housing.
The electron gun is a two stage non-selected gun designed by Woolf (Ph.D thesis, University of Manchester) (see figure 3). The gun consists of a filament, grid and anode source which is focussed using a triple aperture lens through two 1mm defining apertures in the centre of the gun. The apertures define the electron beam pencil and beam angles, and are focussed onto the interaction region using a second triple aperture lens located between the apertures and interaction region. The electron gun is shielded using advance (constantin) sheet which is grounded to the body of the gun mounting. The gun is mounted onto an x-y translation table to allow placement of the electron beam as accurately as possible to the centre of rotation of the analysers and electron gun rotation axis.
The gas jet is mounted from the electron gun using a narrow support of 310 stainless steel, and the Faraday cup can be attached to this support. The original unselected electron gun built by Woolf was completely rewired and a custom built PTFE 25 way inline wire-wrap plug and socket was placed between the 52 way vacuum electrical feedthrough and the electron gun. The wiring from the 52 way feedthrough to the inline plug is shielded colour coded 30 awg PTFE coated advance wire, and the inline plug and socket connectors are non-magnetic gold plated wire wrap pins.
The electron analysers are constructed from molybdenum and are mounted from two rotating gear plates controlled externally via the rotation feedthroughs on the top flange (see figure 2). The input electrostatic lenses for each analyser are three element cylindrical lenses as shown in figure 4.
The interaction region is focussed onto the entrance aperture of the hemispherical energy analysers with a beam angle of around zero degrees, the image of the analyser entrance aperture being larger than the size of the interaction region.
Field gradients around the input and exit apertures are corrected using standard Jost correctors.
The energy selected electrons passing through the exit apertures are finally collected by Mullard X919BL channel electron multipliers which amplify the single electron to produce a current pulse at their output. A principle source of noise on the signal pulses arises from the turbo-molecular pump motor. The noise from the turbo pump is reduced to ~ 5mV using these techniques, and as the average pulse height from the saturated multiplier is around 20-40 mV, this allows adequate discrimination following amplification. The pre-amplifiers located external to the vacuum system are commercial 100X preamplifiers with 400pS rise-times, manufactured by Phillips Scientific. The NIM signals produced by the discriminators drive two ORTEC 437 Time to Amplitude Converter's via appropriate delay cables and an ORTEC pulse delay unit.
The main TAC output feeds an ORTEC Multichannel Analyser card located in the PC controlling the experiment, whereas the second monitor TAC drives an external MCA, allowing convenient monitoring of the coincidence signal as the experiment progresses.
The high voltage supplies to the electron multipliers are two Brandenberg 5kV supplies controlled by the main PC via serial DAC's. Principally the filter is used to reduce pickup noise from entering via the HT cable onto the multiplier output. Secondly, the filter has a slow response time for high voltage spikes, and reduces the probability of damage to the pulse electronics should the EHT supply suddenly turn on or off.
Capacitor C2 decouples the 1kW load resistor to earth for high frequency pulses from the CEM's, and the voltage appearing across this load is connected via the capacitor C3 to the input of the 6954 preamplifier. Since the input impedance of the preamplifier is 50W and the CEM is effectively an ideal constant current supply, most of the current passes through to the preamplifier. Finally, the 10M resistor prevents the output to the preamp from rising above ground when the preamp is disconnected from the circuit and is therefore a safety device for the preamplifier when initially connected. The original design placed the atomic beam nozzle and Faraday cup on the same support structure fixed to the body of the electron gun, with the atomic beam direction being in the detection plane when the perpendicular plane geometry is chosen (see figure 2). A second configuration is adopted for exclusively perpendicular plane coincidence experiments, the atomic beam nozzle being oriented at an angle of 45A° to the detection plane so that the gas effusing from the nozzle does not fill the analysers when they oppose the nozzle (see figure 6). In this configuration the support strut for the atomic beam nozzle is terminated lower than the detection plane, as is the nozzle itself. For non-perpendicular plane measurements the Faraday cup is once mounted from the support strut and the gas effuses perpendicular to the electron beam direction.
One difficulty when aligning an (e,2e) coincidence experiment lies in the focussing the incident electron beam and analysers onto the interaction region. The throughput of electron current as detected by the Faraday cup is insensitive to both position and focusing of the electron beam, since the cup opening is usually made quite large (in this case 6 - 10mm) and the bias voltage applied to the cup to prevent electrons returning to the interaction region allows all electron trajectories within this opening to be detected. Conventionally, following maximisation of the Faraday cup current, the beam is steered and focussed onto the gas jet as detected by counts in the analysers.
This has the disadvantage that the overlap volume is maximised for both atomic and electron beam density, which tends to place the interaction volume as close as possible to the output of the atomic beam nozzle, which is almost certainly not in the centre of the detection plane.
To eliminate the need for time consuming iterative techniques and the associated errors due to detection geometry, a separate method for tuning the electron gun is adopted that does not depend upon the analysers. The interaction between the target and the electron beam not only produces ionisation, but the valence states of the target also are excited with various probabilities depending upon the incident energy of the electron beam. These photons are detected by the photomultiplier tube, by placing a 450nm A± 50nm optical filter in front of the photocathode. The interaction region is therefore defined where an aperture in front of the photocathode is focused by the lens. The plano-convex focussing glass lens is covered by a grounded fine tungsten mesh to eliminate surface charging. The photomultiplier tube may be cooled by circulating nitrogen gas boiled off LN2 through copper coils encircling the photomultiplier tube housing.
The photomultiplier tube used in the experiment is a 9789QB EMI photomultiplier tube with a bi-alkali photocathode peaking in the blue region of the optical spectrum. As with the electron multiplier circuitry, it is important to optimise the load of the photomultiplier tube so that reflections along the feeder line to the counting electronics are minimised. The 1nF 6kV capacitors across the dynodes close to the output stage are used as charge storage pumps that quickly refurbish the surface charge on the dynodes, allowing increased counting rates. The dynode resistors are 1% tolerance metal film resistors as these are more stable with temperature.
The EHT supply to the photomultiplier tube is a Brandenberg 2kV supply operating at 1500V for this tube. The negative going output pulses from the tube measure typically 200-500mV in height, and therefore are able to directly drive an ORTEC 473A constant fraction discriminator located in one of the NIM crates.
All resistors and capacitors for the dynode chain are soldered to the photomultiplier tube base internal to the vacuum system, using standard 5-core solder. Typical pulse heights from the electron multipliers in saturation mode are 25-40mV, whereas the typical height of the photomultiplier tube pulses is of the order of 250mV.
The electron multiplier pulses are obtained from the multiplier supply circuitry as explained above. The amplified pulses from the 6954 amplifiers pass along doubly shielded RG-58 cable to the input of the ORTEC 473A discriminators. The two analyser discriminators are located in separate NIM crates to increase isolation and reduce common mode pickup. The slow rise-time positive outputs from the 473A discriminators pass to three ORTEC 441 rate-meters which allow counting and monitoring of the pulses. The fast NIM pulses from the analyser 473A CFD's pass through appropriate delay lines to two 437 TAC's. This second multichannel analyser allows the operator to monitor the total accumulated coincidence signal during operation. The lens supplies that control the voltages impressed onto the lens elements and deflectors in the experiment were developed over a number of years, and therefore take different forms. Three of these supplies feed the deflectors in the electron gun, the other two supply the input deflectors in the analysers. In a second 19" crate is located the gun lens high voltage supplies together with the high voltage supplies for the Faraday cup.
In a third 19" crate is located the analyser voltage supplies together with a set of serial loading supplies that control the electron multiplier EHT supplies. A further supply controls the current boost circuitry located in the filament constant current supply unit (see below). The outputs of each computer controlled supply that drives an individual lens element or deflector are connected to a 70 relay switching board.
The Digital voltmeter is in turn accessed via an IEEE-488 interface which is addressed by an 8086 slave PC which converses with the central PC which controls the experiment. The outputs from the relay board connect to the spectrometer via shielded multicore cables which take the gun voltages to the 52 way feedthrough and the analyser voltages to the two 19 way feedthroughs located on the vacuum flange. The gun supply multicore also carries the filament supply current to the 52 way feedthrough. The Faraday cup current is measured by the Keithley Digital voltmeter when under computer control but this can also be measured by an external pico-ammeter. In addition to the analyser electrostatic lens and deflector voltage connections, the 19 way CF70 feedthroughs are used to control signals from internal sensing opto-isolators which control the stepper motor interlocks. The stepper motors that drive the analysers and electron gun around the detection plane are five phase motors with integral 10X reduction gearboxes driving the rotary motion feedthroughs. The intelligent stepper motor drivers are addressed via a serial port located on the controlling PC bus. An additional interference problem was traced to the RS232 serial line from the controlling PC.
The PC bus was found to be poorly earthed due to very little copper being used for the bus earth.
This was cured by decoupling the 0V RS232 line from the main 0V line for the stepper motors, as is shown in figure 10. The analyser stepper motor supplies have a facility for halting the motors using limit switches which are optically coupled to the internal 68000 logic circuits driving the supplies.

The SD5443-3 phototransistor normally illuminated by the TEMT88PD photodiode during operation ensured a fail-safe mechanism should any of these components fail (this automatically prevent the motors from running).
Should the analysers move into a position as defined by the four criteria (a) - (d) above, a shutter located on the analyser turntables moves between the appropriate photodiode and phototransistor, shutting off the light and thereby shutting down the stepper motor current.
Only motion in the opposite direction is allowed by controlling logic, allowing the analyser to move away from the point of imminent collision but no closer. The six pairs of optocouplers that prevent the analysers moving into the Faraday cup, electron gun and gas jet support are located on the mounting struts supporting the main body of the spectrometer.
Two optocouplers are located on the side of analyser 2, and two shutters are located on the sides of analyser 1 to prevent the analysers colliding with each other. Finally a ninth optocoupler is located over the electron gun counterweight which monitors when the gun is at an angle less than 65A°, where the sweep angle around the detection plane is reduced. The current boost circuit operates from a serial driven supply card as detailed previously. The main filament drive is through six power diodes that feed the current from the constant current supply to the filament. The Darlington transistor T1 feeds additional current to the filament via three parallel 10 turn 100W trim resistors through a 1N4007 diode.
As the constant current supply acts as an infinite resistance source, the boost circuit supplies additional current only when the voltage at the anode of the feed 1N4007 exceeds the output voltage of the constant current supply.
Finally, the filament bias voltage (and hence energy of the electrons) is set to the midpoint of the filament by two 100W balancing resistors located across the terminals. In addition to the ADC buffer card, three independent isolated regulated supplies drive REF01 voltage reference sources for measurement of the positions of 10 turn potentiometers located on the analyser and electron gun rotary drive shafts. The angular position of the electron gun and analysers is calibrated when the system is opened using visible laser diodes that define these angles to an accuracy of A±0.2A°. Figure 13 shows an overall block diagram detailing the computer control and high speed pulse interfacing to the spectrometer. Shielding is a fast way to comply with legal requirements like CE or FCC or to prevent electro-magnetic interference.
Corrosion protection is very important for applications near to the sea (due to salt) and in outdoor applications. We have designed special resilient gaskets, such as Ultra Soft Shield and V-shape gaskets.
To give you an idea of what kind of gasket would be suitable for your application, you can send a drawing (preferably including dimensions, quantity needed, materials of the enclosure and indication of stiffness of enclosure material) to our specialists. We can produce our gaskets in any desired quantity, whether it is just one gasket or a thousand, and all gasket can be made to your specifications.
The conductive layer on the outside of the gasket needs to be in the same galvanic range as the construction materials, otherwise galvanic corrosion will occur and the electrical conduction within the structure will be lost. Aluminium housings:When you need to EMI-shield an aluminium housing, we recommend using 6800 series Amucor shielding gaskets. To obtain a contact surface within the same galvanic range as the conductive covering of the gaskets, a Conductive Tape with a conductive self-adhesive on the back can be applied. Another way to avoid galvanic corrosion is to prevent corrosive environmental influences from reaching the EMI shielding gasket, for example by the means of a gasket that combines a water seal with EMI shielding (fig. Some manufacturers of EMI shielding gaskets use layers containing carbon on the outside of the gasket to prevent corrosion. For high frequencies (HF shielding > 40 MHz), only a very thin layer of highly conductive material would suffice.
The allowed stiffness of the gasket depends on the rigidity of the construction and the distance between the fixings. For shielding doors and lids, it is important that you use a gasket with the correct resiliency. For conductive metal Faraday cage doors, a 8700 series V-shape gasket or 2000 series Be-Cu Fingerstrips is most frequently used.
For applications where a relatively small and watertight gasket is required, we can deliver 5750 electrically conductive rubber o-profiles. Not only connections between construction parts, but also displays and vent panels need to be shielded. The shielding of the displays will have to be connected with the shielding of the enclosure to guarantee optimal attenuation.
To prevent radiation from escaping the shielding through power and signal cables, they need to be shielded or filtered. The shielding of the cables always needs to be properly connected to the shielding of the enclosure; otherwise the shielding will have a lower (possibly insufficient) attenuation level. Please note that cables without a shielding jacket need to be shielded outside the shielded enclosure as well to prevent them from acting like antennas.
Shielding PCBs and shielding individual components can also be achieved by soldering vertically placed metal strips (e.g.
If the radiation source or the EMI sensitive component is known, shielding for the specific component(s) can be applied. For some applications, it is desirable to shield an entire room by attaching metal foils, such as Mu-copper foil, to the walls. Almost any electrical transitions with sharp edges, such as clocks, data, address and control, produce electromagnetic radiation.
Worldwide leading manufacturer of EMC (electromagnetic compatibility), EMI (electromagnetic interference) and RFI(radiofrequency interference) shielding solutions. Keep up to date with the latest developments in Holland Shielding Systems BV by signing up for our newsletter.
United Western Enterprises is experienced in developing, manufacturing and improving custom RFI and EMI shielding. One piece shielding, shielding with peel away tops or two piece shields consisting of a a€?fence and covera€? combination are typical designs for shielding. One of these is internally connected to a gas jet which can be set at 45A° to the incident electron beam and is used in the perpendicular plane experiments. These stainless steel feeder tubes are connected to the nozzle using grounded shielded PTFE hose.
One follows the anode, another corrects the beam direction between the apertures and a third steers the beam onto the interaction region. This shield is coated with aerodag colloidal graphite to reduce patch fields on the surface of the metal, and is made as small as possible to allow the analysers to approach the gun as close as is feasible when non-perpendicular plane geometries are selected (see figure 2). The XY translation table is mounted from the rotating yoke, to which is attached the photomultiplier tube. This allows the gun to be dismounted from the system without the need for rewiring of the feedthrough when the need arises (filament changes, cleaning etc). The wiring between the gun and inline socket is also shielded colour coded PTFE coated advance wire facilitating spot welding to the electrostatic lens elements of the gun. The analysers are mounted onto x-z translation tables that allow them to view the interaction region accurately over the full range of angles accessible. These lenses have a capability for energy zooming of around 10 : 1, and have a maximum entrance acceptance angle of A±3A° as defined by the entrance apertures. This ensures that the overlap volume accepted by each analyser encompasses the interaction volume for all detection angles as the analysers move in the detection plane. These devices use an activated lead glass internal surface which has a high coefficient of secondary electron emission when a high voltage (around 3000V) is applied across the multiplier. This noise may be picked up by the channel electron multiplier and the high voltage feed to the multiplier, and is generated internally in the vacuum system.
The CFD's are operated in NaI mode as this has a 2ms dead time following the initial pulse, thus reducing the possibility of false triggering due to any mismatching impedance reflections along the delay cable. These EHT supplies are connected via VERO 200 high voltage couplings to high voltage cable connecting to the pickoff circuitry located on the high voltage feedthroughs. This allowed the analysers to roam the detection plane over a complete 360A° angular range. The configuration of the target source hypodermic when perpendicular plane measurements are conducted. The common procedure is to initially maximise the current from the gun onto the Faraday cup, then onto analyser counts as the electron beam is moved through the gas jet.
Maximising the Faraday cup current is therefore only a crude preliminary alignment of the incident electron gun beam.
This therefore assumes that the analysers are initially focused onto the interaction region, and a slow iterative technique must be adopted where the analysers and electron gun are tuned so as to maximise the signal from both analysers.
In this case a true differential cross section is not obtained, since the scattered and ejected electron trajectories lie in a different plane than defined in the initial experimental alignment. An EMI 9789QB reduced photocathode photomultiplier tube is installed in the vacuum system together with optical focussing and defining elements (figure 2). A group of these excited states decay back to lower valence states with the emission of visible photons at wavelengths around 450nm for both helium and argon targets. Tuning of the electron gun to PMT counts therefore guarantees that the electron gun is steered and focussed to the point at the centre of the detection plane independent of the analysers or gas beam density. This is mainly used when the vacuum system is baked at temperatures above 55A°C, since the photocathode is rapidly damaged by temperatures exceeding this. The tube is a venetian blind dynode construction, and has a reduced photocathode to decrease the noise on the output of the tube to less than 20Hz. The photomultiplier tube base was thoroughly cleaned in an ultrasound following location of these components, to displace any flux residue from the solder joints. It is therefore necessary to amplify the channeltron pulses prior to transmission to the discriminators, whereas the photomultiplier tube pulses are sufficiently large to not require further amplification. These pulses are amplified by Phillips Scientific 6954 100X amplifiers located external to the EHT feedthroughs connected by 10cm lengths of RG-58 cable. These crates are further decoupled from the AC mains supply using filter circuitry on each supply line. Internal to these rate-meters buffer 7400 TTL chips have been added to send to 32 bit counters located in the main PC via RG-58 cable. These supplies are fully floating, their mid-point voltage being equal to the lens element voltage in which the deflectors are housed. All these supplies are fully computer controlled isolated units with low output impedance to reduce noise and eliminate current loops. This relay switching unit allows either the voltage or the current on each lens element to be measured by a Keithley Digital voltmeter. This drive is further reduced internally by 10X reduction gears, resulting in a reduction ratio of 100:1. This led to the ground line of the RS232 serial line moving around with respect to the 0V stepper motor reference as drive current to the motors returned along the ground line.
The optocoupler logic circuit circuit that controls the stepper motors and avoids collisions between the analysers, the electron gun, the Faraday cup and the hypodermic support. Added to this filament supply is a computer controlled current boost circuit that can be used to increase the filament current during electron gun tuning. The additional current then returns to the 12V DC regulated supply via a second 1N4007 diode. This therefore depends upon both the current driving the filament, as well as the resistance of the filament when hot (typically 4W - 6W). This supply feeds current to the filament without changing the characteristics of the main constant current supply used while operating the spectrometer.

These high stability reference sources ensure that the analyser and electron gun positions are accurately measured with time. A datalogger internal to the controlling PC establishes a cubic spline relationship between the measured angles and the corresponding ADC conversion from the potentiometers.
This PC also controls the selection of the relay motherboard for measurement of the required lens element either in voltage or current mode when a request is sent from the controlling computer via an RS232 serial line. Adesso stai seguendo mu-metal nel tuo Feed.Riceverai notifiche tramite email per le nuove inserzioni.
The use of electronical devices increases as well as the exposure to a wide range of frequencies.
Our shielding solutions are cost-effective, since time-consuming development is not required to meet EMI demands. At lower frequencies, such as 30 kHz and less, it is important to use materials with a good magnetical (and electrical as well when dealing with eddy currents) conductivity and possibly a thicker material will be needed as well. High frequencies, ranging between 100 MHz and 40 GHz, are very sensitive to small gaps in the enclosure. Our specialists are experienced with all sorts of shielding applications and take a look at over 50 designs on a daily basis. To shield the vents (ventilation openings), we recommend using 9500 series Honeycomb ventilation panels. If the enclosure is to be painted, the tape can be provided with a masking tape of a slightly smaller width (the paint will cover the conductive tape along the edges, which increases bonding and corrosion resistance) (fig. Please be aware that these carbon layered gaskets are not galvanically compatible with many commonly used construction materials.
If the gasket is too stiff, a door, lid or panel will deflect and gaps will be caused instead of prevented (fig. Displays can be provided with a sputtered transparent conductive coating for HF shielding (>30 MHz, fig.
Shielding can be provided by covering the cables with shielding tubes or by wrapping conductive materials around the cable. For heavy duty and military applications, shielded cable glands and specially designed cable entry systems are available. Preventing such a leak in the EMI-shield can be done by installing a power- or signal line filter or, in case you are dealing with shorter cables leading to another shielded enclosure, using a wrap-shield or shielding tube. 9) made of Mu-copper shielding foil with an insulation layer on the inside or with plastic studs to avoid short-circuiting (fig. The best way of shielding at the source is to shield only the interfering part or the sensitive part on the PCB with our specially developed 1500 series PCB shielding system.
Think of medical and military applications and rooms to make very sensitive measurements in.
The spectrometer is shown configured in the perpendicular plane, the electron gun being placed in the vertical position with respect to the analysers which span the horizontal detection plane. The electron source is a heated tungsten hairpin filament heated by passing around 2A of DC current through the filament. The saturated gain of these devices yields around 1E8 electrons in the output current pulse for a single electron which enters the input cone. This allows the analyser to roam over a complete 360 degrees of the detection plane when in this geometry (apart from the position where the analysers would clash wth each other). The analysers are then adjusted for maximum signal count and the procedure is iterated until a maximum is found. The dark noise count is also reduced when cooled, however since the reduced cathode PMT only produces dark counts of less than 20Hz at room temperature, this is not necessary during routine operations.
The 1.82M resistor was chosen to optimise the single photon counting efficiency of the tube.
It is not found that these solder connections significantly affect the ultimate vacuum pressure in the system. Isolated DC supplies to these amplifiers is obtained from a standard +15V supply, the circuit diagram being given in figure 8.
The power supply to these TTL buffers is derived from the rate-meter supplies via 7805 5V regulators located internally. This supply boosts the current without changing the main supply, thus ensuring supply stability before and after the electron gun is tuned.
Radiation and immunity has to be taken into account in an early stage during the development of new products.
Shielding is typically used in enclosures in order to isolate electrical devices inside from external influences and for cables in order to isolate wires from the environment through which the cable runs. If shielding against frequencies around 50 Hz is required to limit influences from a transformer (that can cause health risks or influence the operating system of machines), then using dense metal layers and a special material called Mu-ferro should be considered (see magnetic shielding). The higher the frequency, the more attention should be paid to prevent holes and gaps in the shield. They are a cost-effective solution since no fundamental changes to the enclosure have to be made and there is no need for extra fasteners. They are specialized in picking the right type of gasket for any application and their advise is without charge.
To prevent influences from lower frequencies, cables and enclosures have to be shielded with magnetically conductive materials. In other words: doors, panels and other parts need to be connected electrically, on all sides (without gaps). We have developed two different cable entry shields, one consisting of two fringed EMI gaskets on the top- and bottom side of a slot (4910 - Cable entry shield) and the other consisting of a contact plate (to be mounted in front of a slot) with holes for cable througput (4930 - High Performance cable entry shield). They consist of a 1mm thick die-cut material, which can be manufactured easily according to customer specifications, with little additional tooling costs (fig. These compartments are closed by adding a lid of flexible die-cut shielding foil or by pressing a soft conductive foam sheet against the strips (fig. The technique may even be applied in forensic science, for example if a device needs to be blocked completely from communicating with the outside world while being examined. To make it easy for you which IP rating you need for the desired result we have put all the IP rating in a clear table. The transition edge, or in engineering terms, the slew rate, has become faster and faster as the need for meeting set up and hold time has become harder to meet. Shields can be etched as flat pieces with or without etched bend lines to ease forming at your facility or we can form at our in-house forming department. The electron gun is a two stage non-energy selected gun that produces an incident electron beam current of up to 4 microamps at an incident energy from around 30eV to 300eV. The 470k resistors bias the dynodes to achieve saturation of the current pulse at the output of the tube, hence biasing the tube for single photon counting applications. This was found to be necessary to eliminate problems associated with current loops from the 20A peak motor current feeding the common point of the logic circuitry. In many cases EMI problems cannot be solved at PCB level alone and instead, the enclosures and cables will have to be shielded as well. If a quick market introduction is intended and the emission exceeds the set limits, easy-to-apply shieldings are a commonly used solution.
However, EMI shielding gaskets with a conductive layer of reinforced Amucor® foil are compatible with materials like zinc plated steel and aluminium. Especially for doors, several kinds of gaskets have been developed which combine a very large compression range, a low closure force and high conductivity. A shielding tube consists of hollow braided metal wire, through which the cable or bundle of cables can be pulled in order to shield it. Part numbers, logos or other identification can be included on your shields as well, further developing the shielding to your requirements. The analysers are identical, and consist of a 3-element electrostatic lens focussing the interaction region onto the entrance of a hemispherical electrostatic energy analyser. The Anode deflector pair corrects for any misalignment of the filament emission point with respect to the axis of the electron gun.
Shieldings can be used for appliances with high radiation levels, sensitivity levels or for products of which these levels are not known in advance, like modular enclosures.
When the enclosure is used in a corrosive atmosphere, it is better to prevent contact with stainless steel, brass, or an aluminum chromate layer (alocrom 1200).
The transparent conductive coating is delivered on foil (bendable and easy to stick onto a window), glass (standard window) or other materials (for heavy-duty purposes). A wrapshield is a knitted metal wire tape, which is wrapped around a cable or bundle of cables. Though the plate system has a higher performance, the fringe system is easier for adding cables later on.
The Chamber is lined internally with 3mm thick mu-metal, and a mu-metal cylinder encloses the chamber externally as shown. The electrons selected in angle and energy are amplified using Mullard 919BL channel electron multipliers. The defining apertures limit the pencil and beam angles of the electron beam following focussing by lens 2 onto the interaction region. The load is set by the 50W resistor across the anode to the HT feed, the pulse being decoupled to ground via the 1nF capacitor. Shieldings are used when dealing with sensitive measurements that can be affected by ambient fields as well. The gasket selection diagram below could be very helpful in determining the appropriate gasket material. Honeycombs are usually supplied with a rigid aluminium frame and a gasket of 2-5 mm for optimal connection with the construction. It is easier to create branches with the wrapping method than it is to create branches with shielding tubes.
This reduces the magnetic field at the interaction region to less than 5mG, an acceptable level for the electron energies used in this experiment. The interaction region defined by the interaction of the gas target beam and the electron beam is focussed onto the photocathode of an EMI 9789QB photomultiplier tube via a lens, 450nmA±50nm optical filter and defining aperture. Placement of the apertures ensures that the beam angle is close to zero degrees at the interaction region over a wide range of energies, whereas the aperture opening reduces the pencil angle to around A±2 degrees over this energy range.
Shielding is evidently a wide-spread phenomenon and necessity in the electronics industry to meet today's emission standards. The target gas effuses from a 0.6mm ID hypodermic needle constructed from platinum iridium alloy. The 10MW safety resistor prevents the output charging up to a high voltage if the feed is disconnected. The deflectors between the apertures correct for space and surface charge beam variations inside the field free region, whereas the final deflectors allow the beam to be steered onto the interaction region defined by focussing a 1mm aperture in front of the photomultiplier tube onto the gas target beam. The electrons passing through the interaction region which are not scattered are collected in a Faraday cup opposite the electron gun.
The gun, photomultiplier tube, gas hypodermic and Faraday cup all rotate on a common yoke with an axis through the centre of the horizontal detection plane, allowing all geometries from the perpendicular plane to the coplanar geometry to be accessed.

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