Surface Concept MCPD25 User manual

1-Channel MCP Detector MCPD25 Manual
1-Channel MCP Detector
MCPD25
(Release 009 & 012)
Manual

21-Channel MCP Detector MCPD25 Manual | Surface Concept GmbH
Surface Concept GmbH
Am Saegewerk 23a
55124 Mainz
Germany
phone: [phone]
fax: [phone]
email: [e-mail]
web: www.surface-concept.de
All rights reserved. No part of this manual may
be reproduced without the prior permission
of Surface Concept GmbH.
1-Channel MCP Detector MCPD25
Release R009 & R012
Manual Version 2.0
Printed on 2020-10-22

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1 Table of Contents
1 Table of Contents ......................................................................................................................3
2 Introduction................................................................................................................................5
2.1 General Information..........................................................................................................5
2.2 Safety Instructions .............................................................................................................5
2.3 General Overview of the System..................................................................................6
3 Installation...................................................................................................................................7
3.1 Initial Inspection.................................................................................................................7
3.2 Installation............................................................................................................................7
3.2.1 Mounting the MCP Detector...............................................................................7
3.2.2 Cabling and High Voltage ....................................................................................8
4 Operation of the MCPD ..........................................................................................................9
4.1 Getting Started ...................................................................................................................9
4.1.1 “Start Up“ Procedure ..............................................................................................9
4.1.2 Dark Count Rate Measurement....................................................................... 11
4.1.3 Standard Detector Measurement....................................................................11
4.2 Standard Operation Procedure.................................................................................. 11
4.2.1 Operation with MCP Front Side terminated to GROUND........................11
4.2.2 Operation of the Detector with the MCP Front Side connected to a
Reference Voltage................................................................................................12
4.3 Bake Out Procedure....................................................................................................... 14
5 MCP Detector Layout ........................................................................................................... 15
5.1 MCP Detector - Vacuum Wiring................................................................................. 15
5.2 MCP Detector - Connection Ports ............................................................................ 15
6 Microchannel Plate ............................................................................................................... 17
6.1 Specifications................................................................................................................... 17
6.2 Storage............................................................................................................................... 17
6.3 Handling............................................................................................................................ 17
6.4 Operation.......................................................................................................................... 18
6.5 MCP Lifetime and Operation Voltage ..................................................................... 18
6.6 MCP Degas Procedure.................................................................................................. 22
6.7 Replacement.....................................................................................................................22
7 Technical Data......................................................................................................................... 23
8 List of Figure ............................................................................................................................ 25

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This side has been left blank on purpose.

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2 Introduction
2.1 General Information
This manual is intended to assist users in the installation, operation and maintenance of Release Version
009 & 012 of the 1-channel MCP detector MCPD25.
It is divided into 8 chapters. The chapter “Introduction” contains a brief description of the Detector.
The chapter “Installation” refers to installation and cabling. Chapter “Operation of the MCPD” describes
the operation of the detector. The final chapters contain amongst others technical details about the
microchannel plates and the MCP detector in general.
2.2 Safety Instructions
Please read this manual carefully before performing any electrical or electronic
operations. Strictly follow the safety rules given within the manual.
The following symbols appear throughout the manual:
Note
The“note symbol”marks text passages, which contain important information/hints about
the operation of the detector. Follow these information to ensure a proper functioning
of the detector.
The “caution symbol” marks warnings, which are given to prevent an accidentally
damaging of the detector or the readout system. Do NOT ignore these warnings and
follow them strictly. Otherwise no guarantee is given for arose damages.

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2.3 General Overview of the System
The Surface Concept MCPD25 is a 1-Channel MCP Detector for counting detection of electrons, ions, x-ray
and UV-light. It is a non imaging device, but it can be used with the appropriate readout electronics for
time resolved measurements.
The MCPD25 R009 is mounted on a CF100, the MCPD25 R012 on a CF160 vacuum flange with feedthroughs
for high voltage supply and signal transfer. It consist of a chevron microchannel plate stack and a single
metal anode. The anode as well as the signal feedthrough is a 50Ohm matched system.

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3 Installation
3.1 Initial Inspection
Visual inspection of the MCPD25 is required to ensure that no damage has occurred during shipping.
Should there be any signs of damage, please contact your provider immediately. Please check the delivery
according to the packing list (see Table 1) for completeness.
• MCP Detector Unit (delivered in a vacuum container)
• 1x SHV Termination Plug
3.2 Installation
The detector is packed under vacuum. Proceed as follows, to install it into your vacuum chamber:
• Vent the package carefully and slowly (use N2 for venting if possible).
• Remove the transport container carefully.
• Before installing the detector to your chamber, check the front side of the MCP stack for particles.
3.2.1 Mounting the MCP Detector
The microchannel plates in front of the detector should be protected from exposure to
particle contamination. Particles that stick to the plate can be removed by using a single-
hair brush carefully and/or with dry nitrogen. Reading the instructions “microchannel
plates” in Chapter 6 is strongly recommended.
Table 1: Packing list for the MCP detector.
• Install the detector into your vacuum chamber.
• Keep the vacuum container in case that the detector must be sent back for repair. It can also be used
to store the detector when not installed in a vacuum chamber.

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3.2.2 Cabling and High Voltage
The general connection scheme of the MCP detector is shown in in Figure 1.
Figure 1: Connection scheme of the MCPD25.
• The detector holds two SHV connectors for the high voltage supply named “MCP-B” and “MCP-F”. The
naming can be found directly engraved on the flange. “MCP-F” is the contact to the front side of the
MCP stack, “MCP-B” is the contact of the detector anode and of the back side of the MCP stack via an
internal resistor.
• Signal readout is realized via a single, 50Ohm matched BNC feedthrough named“SIG”. The naming can
be found again directly engraved on the flange.
Be sure that all voltages are settled to zero before connecting the high voltage cables to
the detector, otherwise serious damage to the detector can occur due to high voltage
sparks.
The detector should be kept under vacuum all the time.
The best long term storage environment is an oil free vacuum in the 1E-2mbar range or
better. The transport container is not designed for a long term storage of the detector. A
storage time of one month should not be exceeded.
The transport housing should be evacuated regularly with a period of at least one month,
in case that the transport housing must be used for a longer storage time.
Note

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4 Operation of the MCPD
4.1 Getting Started
Follow this procedure when taken the detector to operation the rst time and after every venting.
• Finish the complete cabling as described in Chapter 3.
• Be sure, that the vacuum pressure at the detector is remarkably below 1E-6mbar, otherwise the
microchannel plates might be damaged by a local discharging (in general: the lower the pressure, the
longer the lifetime of the MCPs).
4.1.1 “Start Up“ Procedure
Ion gauges and ion pump are both sources for electrons and ions. Ion pumps can also
be a source for X-rays. They can produce so many particles/X-rays that the detector is in
a complete overload, even when they are not facing the detector directly. This will wear
out the MCPs very fast. Turn o ion pumps and ion gauges before turning on the high
voltage of the detector.
• Turn on the high voltage carefully. The voltage increase should not exceed 400V per minute. A
schematic sketch on how to ramp the voltages during the “Start-Up” procedure is given Figure 2. The
starting operation voltage is specified in the specification sheet of the detector.
• Watch the vacuum pressure while increasing the high voltage; turn the voltages back, if an unusual
increase is observed in the pressure (indicator for high voltage sparking).
Mistakes, which lead to complete wrong measurement results, can happen very easily
while taking the detector to operation. Therefore it is strongly advised to read the
following sections completely before taking the detector to operation and to strictly
follow all given advices within it.
All operation voltages for the detector are given within the detectors specication sheet.
Due to gain degradation it will become necessary to increase the operation voltage from
time to time. Please refer to Chapter 6.5 for detailed information.
Note

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Figure 2: Schematic sketch on voltage ramping during“Start-Up”procedure.
Note
The detector starting operation voltage for “MCP-B” is given in the specication sheet.
The voltage for “MCP-B” is always given in reference to the MCP front voltage “MCP-F”.
Example: Assume the following operation voltage for“MCP-B”: +1800V.“MCP-F”is terminated to GROUND.
Use a ramp time of approx. 5min. to increase“MCP-B”to +1800V.
High voltage sparks may seriously damage the detector anode or the MCPs. Observe the
chamber pressure carefully every time the high voltage is turned on. Switch o the high
voltage immediately in case of a temporary pressure rise by an order of magnitude or
more. This indicates high voltage sparking.
If sparking occurs, turn down the high voltage immediately and wait some time (up to
5min.). Start the “Start-Up” procedure again with an increased ramp time. Turn o the
high voltage completely, stop the procedure and call your provider for further assistance,
if is it not possible to reach the operation voltage without sparking.

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4.1.2 Dark Count Rate Measurement
• Check the detector output by means of any electronics and software or with an oscilloscope where the
input is terminated with 50Ohm.
• The dark count rate without any source should be as given in the specification sheet.
4.1.3 Standard Detector Measurement
• After finishing the dark count rate measurement with a satisfying result, you may now start carefully
with an electron or light source observing the detector output.
Turn o the high voltage before performing any changes of the cabling.
Use this procedure for all later operation when the detector has already been operated in vacuum
before and has not been vented in between.
• Finish the complete cabling as described in Chapter 3.
• Be sure, that the vacuum pressure at the detector is remarkably below 1E-6mbar, otherwise the
microchannel plates might be damaged by a local discharging (in general: the lower the pressure, the
longer the lifetime of the MCPs).
• Turn off all sources for electrons, ions, light or X-rays that might hit the detector.
• Turn up the high voltage carefully and stepwise within 2 - 3 minutes to the operation voltage. The
starting operation voltage is specified in the specification sheet of the detector.
• Watch the vacuum pressure while increasing the high voltage; turn the voltages back, if an unusual
increase is observed in the pressure (indicator for high voltage sparking).
4.2 Standard Operation Procedure
4.2.1 Operation with MCP Front Side terminated to GROUND
High voltage sparks may seriously damage the detector anode or the MCPs. Observe the
chamber pressure carefully every time the high voltage is turned on. Switch o the high
voltage immediately in case of a temporary pressure rise by an order of magnitude or
more. This indicates high voltage sparking.

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If sparking occurs, turn down the high voltage immediately and wait some time (up to 5
min.). Start the“Start-Up”procedure again with an increased ramp time.Turn o the high
voltage completely, stop the procedure and call your provider for further assistance, if is
it not possible to reach the operation voltage without sparking.
• Now you may start carefully with an electron source observing the detector output.
Turn o the high voltage before performing any changes of the cabling.
4.2.2 Operation of the Detector with the MCP Front Side connected to a Reference Voltage
Follow this procedure for all later operation starts, when operating the detector with the front side of
the MCP stack connected to an external high voltage potential
• Finish the complete cabling as described in Chapter 3.
• Connect an external reference voltage to the “MCP-F” connector. DO NOT APPLY ANY HIGH VOLTAGE
yet.
• Be sure, that the vacuum pressure at the detector is remarkably below 1E-6mbar, otherwise the micro
channel plates might be damaged by a local discharging (in general: the lower the pressure, the longer
the lifetime of the MCPs).
• Turn off all sources for electrons, ions, light or X-rays that might hit the detector.
• Increase the detector voltage for “MCP-B” to the specified operation voltage stepwise within a couple
of minutes. The starting operation voltage is specied in the specication sheet of the detector.
• Now increase the external reference voltage until reaching the desired voltage for“MCP-F”. (Important:
Respect the maximum reference voltage for “MCP-F”. It is given within the specification sheet.) The
voltage increase should not exceed 400V per minute, when operating the detector with an external
high voltage applied to “MCP-F” for the first time. Otherwise turn up the high voltage carefully and
stepwise within a couple of minutes to the operation voltage.
• Increase the external reference voltage until reaching the desired voltage for “MCP-F”.
• A schematic sketch on how to ramp the voltages is given in Figure 3.
• Watch the vacuum pressure while increasing the high voltage; turn the voltages back, if an unusual
increase is observed in the pressure (indicator for high voltage sparking).
High voltage sparks may seriously damage the detector anode/meander or the MCPs.
Observe the chamber pressure carefully every time the high voltage is turned on. Switch
o the high voltage immediately in case of a temporary pressure rise by an order of
magnitude or more. This indicates high voltage sparking.

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• Check the detector output by means of any electronics and software or with an oscilloscope where the
input is terminated with 50Ohm.
• The dark count rate without any source should be as given in the specification sheet.
• Now you may start carefully with an electron source observing the detector output.
If sparking occurs, turn down the high voltage immediately and wait some time (up to 5
min.). Start the“Start-Up”procedure again with an increased ramp time.Turn o the high
voltage completely, stop the procedure and call your provider for further assistance, if is
it not possible to reach the operation voltage without sparking.
The detector operation voltage “MCP-B” is given in the specication sheet. It is always
given in reference to the MCP front voltage“MCP-F”. The maximum reference voltage for
“MCP-F” is also given in the specication sheet.
Note
Example for voltage ramping: Assume the following operation voltage for“MCP-B”in respect to“MCP-F”:
+1,800V and a reference potential for“MCP-F”of +1,000V. A ramp time of a few minutes should be used to
increase “MCP-B” to +1,800V. Then a ramp time of approx. 3 min. should be used to increase the external
reference voltage from 0V to +1,000V in parallel with the“MCP-B” voltage from +1,800V to +1,900V.
Figure 3: Schematic sketch on voltage ramping with external reference voltage.

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4.3 Bake Out Procedure
An exception is the use of a floating HV Supply, where the “MCP-F” is supplied to the MCPD as well as
to a specific reference input of the HV Supply. In this case, the output voltage for “MCP-B” in increased
automatically with applying the reference voltage for “MCP-F”. Surface Concept provides special HV
Supplies with floating capability for such purposes.
Turn o the high voltage before performing any changes of the cabling.
It is strongly advised to read the following sections completely before baking out the
detector and to strictly follow all given advices within it.
The maximum allowed temperature for the detector is 150°C. Do not exceed this
temperature.
Note
• Windows and feedthroughs should be wrapped with aluminium foil, to protect them from rapid
temperature changes.
• The use of heating tapes and jackets is not recommended, due to danger of local overheating.
• Do not remove the blankets until the entire system has thoroughly cooled off.
• Do not operate the detector before the temperature has returned to ambient conditions.
After a bake out, the detector needs at least one day to cool down. If channel plates are
operated at higher temperatures (> 70°C) they can suer damage. Such channel plates
will lose gain and exhibit a markedly higher detector plateau.
Even if the detector housing feels just warm, any internal parts seated on insulators
(e.g. the meander detector) may still be too hot for safe operation. It is imperative that
all users be informed of this issue and take the necessary precaution to ensure proper
device operation.

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5 MCP Detector Layout
5.1 MCP Detector - Vacuum Wiring
The MCP detector MCPD25 consist of a detection area, defined by the MCP holders and the detector anode.
The front side of the detector anode is on high voltage potential, while the signal readout is realized close
to ground potential (in respect to the high voltage of the MCPs). A pulse coupling layer is used to isolate
the detector anode from the high voltage of the MCP stack as well as to couple pulses from the electron
cloud into the metal anode.
Figure 4: Layout of the HV and signal connections.
The base flange of the MCP detector carries two single SHV feedthroughs for the high voltage supply of
the detector and a single BNC feedthroughs for signal transfer (see Figure 4).
5.2 MCP Detector - Connection Ports
The naming of the SHV connections are engraved directly on the flange. The internal high voltage
connection for the detector is given schematically in Figure 5.

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Note
The resistance between “MCP-B” and “MCP-F” (resistance of MCP stack and the internal
resistor) should be in the range of 10 – 60MΩ (the exact value is given in the specication
sheet of the detector). The resistance between “MCP-F” and “SIG” and“MCP-B” and “SIG”
should be unlimited.
Figure 5: Internal connection of the high voltage potentials (schematic).

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6 Microchannel Plate
6.1 Specifications
Please check the specification sheet of the MCPD for the exact MCP specifications.
6.2 Storage
Because of their structure and the nature of the materials used in manufacture, care must be taken when
handling or operating MCPs. The following precautions are strongly recommended:
• The most effective long-term storage environment for an MCP is an oil-free vacuum.
6.3 Handling
• Packages should be opened only under class 100 Laminar flow clean room conditions.
• Personnel should always wear clean, talc-free, class 100 clean room compatible, vinyl gloves when
handling MCPs. No physical object should come into contact with the active area of the wafer. The
MCP should be handled by its rims, there is no solid glass border! Use clean degassed tools fabricated
from stainless steel, Teflon™ or other ultra-high vacuum-compatible materials. Handling MCPs should
be limited to trained, experienced personnel.
• MCPs without solid glass border should be handled very carefully with great care taken to contact the
outer edges of the plate only.
• The MCP should be protected from exposure to particle contamination. Particles which become affixed
to the plate can be removed by using a very pure and low pressure air flow such as from a clean rubber
bellows.
• The MCP should be mounted only in fixtures designed for this purpose. Careful note should be taken
of electrical potentials involved.

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6.4 Operation
• A dry-pumped or well-trapped/diffusion-pumped operating environment is desirable. A poor vacuum
environment will most likely shorten MCP life or change MCP operating characteristics.
• A pressure of 1E-6mbar or better is preferred. Higher pressure can result in high background noise or
even to damaging due to ion feedback or to an electrical breakdown.
• Apply voltages as defined in Chapter 4. If fluctuations appear, damage or contamination should
be suspected and the voltage should be turned off. The assembly should then be inspected before
proceeding.
• Voltage across single MCPs should not exceed the maximum voltage given in the specification sheet of
the detector. Higher potentials may result in irreversible damage.
• MCPs can be degraded by exposure to various types of hydrocarbon materials which raise the work
function of the surface, causing gain degradation.
• Operation at higher temperatures (> 50°C) will cause gain degradation.
• MCPs may degas for quite a while during operation. The pressure increase also depends on the number
of initial particles given to the MCP (e.g. pressure increase from 5E-10mbar up to 5E-9mbar for a new
chevron MCP stack). A degas procedure for MCPs is described in Chapter 6.6.
6.5 MCP Lifetime and Operation Voltage
The lifetime of the MCPs is determined by the MCPs gain degradation over time, whereas the gain
degradation is a function of the extracted output charge. Therefore the lifetime of the MCPs strongly
depends on the count rate applied to the detector over time.
The typical gain degradation of a MCP is shown in Figure 6 as a function of extracted output charge in
terms of coulombs per square centimetre.
Voltages must not be applied to the device while at atmospheric pressure. The pressure
should be 1E-6mbar or lower at the microchannel plate before applying voltage.
Otherwise, damaging ion feedback or electrical breakdown will occur.

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Figure 6: Typical gain degradation of MCPs as function of the extracted output charge.
After an initial burn-in period, in which the detector gain changes as a result of electron induced chemical
allocation together with degassing residual gas molecules from the inside of the channels, the MCP
performance is very stable over a large amount of extracted output charge. The MCP gain is also a function
of the detectors operation voltage. Therefore gain degradation can always be compensated by increasing
the detector voltage.
Detector delivery will still happen with the MCPs operating within the burn-in period, although the detector
has been operated for some longer time with highest count rates during the test phase, Therefore gain
degradation will be still significant in the first year of operation (or even longer, depending on applied count
rates) and becomes obvious by a decline of the detector performance. Therefore it will become necessary
to increase the operation voltage from time to time. Voltage increase should always be made in small steps
(typically 50V). There is a recommended maximum operation voltage, to which the detector voltage can
be increased to compensate gain degradation over time. This voltage is given in the specification sheet of
each detector.
A typical behaviour of the detector voltage increase over time to compensate gain degradation is given
schematically in Figure 7.

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Figure 7: Schematic plot of increasing the operation voltage to compensate gain degradation
over time as function of the extracted charge (all values are only exemplary).
It is not unusual that the operation voltage must be increased several times especially in
the rst year of operation.
Note
Typically, the final operation voltage at the end of the burn-in period will be close to the recommended
maximum operation voltage. An increase of the operation voltage above the recommended maximum
operation voltage is in principal possible and allowed, as long as there is no significant increase in the dark
count rate, bright spots at the detection area and/or appearance of high voltage sparking.
The operation voltage can be increased even above the recommended maximum
operation voltage. A safe and reliable operation will still be possible as long as there is
no increase in the dark count rate and/or no appearance of high voltage sparking.
Note
It can be sufficient to estimate the correct operation voltage by monitoring the detector results, when
increasing the voltage to compensate the gain degradation. The exact operation voltage can always be
determined by measuring a so called MCP curve.The MCP curve plots the detected count rate as a function
of the operation voltage. Do as follows to measure an MCP curve:
• Start the detector operation with a homogeneous illumination (as good as possible).
• Open the rate meter in the Surface Concept GUI Software to monitor the count rate output of the
detector.
• Decrease the operation voltage until the count rate of the detector is reduced to zero.