![](media/image1.png){width="2.4583333333333335in" height="1.375in"}

***BTeV Detector Systems***

***Preliminary High Voltage Requirements***

**BTeV Document (number to be assigned)**

**5 March 2001**

**Revised 27 March 2001**

**Revised 4 April 2001**

**Latest Revision 6 April 2001**

**Editors\
**

David Christian, Ed Barsotti & Robert Downing

[***1** **Introduction 1***](#introduction)

[2 Requirements Common to all Detector Subsystems
2](#requirements-common-to-all-detector-subsystems)

[2.1 Setting and read back 2](#setting-and-read-back)

[2.2 Input and Environment 3](#input-and-environment)

[2.3 Output Characteristics & Connectors
3](#output-characteristics-connectors)

[2.4 Cable Lengths & Remote Sense 4](#cable-lengths-remote-sense)

[2.5 Radiation Tolerance 4](#radiation-tolerance)

[2.6 Packaging 4](#packaging)

[2.7 Maintainability 4](#maintainability)

[2.8 Personnel Safety 5](#personnel-safety)

[2.9 On/Off Control, Fault Monitoring & Safety Interlock Provisions
5](#onoff-control-fault-monitoring-safety-interlock-provisions)

[3 Requirements Unique to Each Subsystem
6](#requirements-unique-to-each-subsystem)

[3.1 Pixel Detector 6](#pixel-detector)

[3.2 Silicon Strip Detector 6](#silicon-strip-detector)

[3.3 Straw Detector 7](#straw-detector)

[3.4 RICH Detector 7](#rich-detector)

[3.5 EM Calorimeter Detector 8](#em-calorimeter-detector)

[3.6 Muon Chambers Detector 9](#muon-chambers-detector)

#  {#section .unnumbered}

# Introduction

This document describes the high-level requirements for BTeV's six
front-end detector high-voltage systems. Most of the high-voltage
systems are likely to require a very large number of individually
controllable voltages. In order to simplify the operation of BTeV, all
of the BTeV high voltage systems must be controllable through a single
control interface. It is highly desirable that all BTeV high voltage
systems be of a single type, differing only in which plug-in modules are
used. The requirements of the various BTeV detector subsystems as they
are currently understood are summarized in Table 1.

+-------+-------+------------+----------+----------+----------------+
| **Det | **    | **\~ Max.  | **V      | **C      | **Readback**   |
| ector | Polar | Channels** | oltage** | urrent** |                |
| S     | ity** |            |          |          | **Precision**  |
| ubsys |       | **(without | *        | *        |                |
| tem** |       | spares)**  | *Range** | *Range** |                |
+-------+-------+------------+----------+----------+----------------+
| P     | Neg   | 1426       | 0-1000   | 10 nA -- | 0.1% of F.S.   |
| ixels | ative |            |          | 10 mA    | V\             |
|       |       |            |          |          | 0.1% of I      |
|       |       |            |          |          | range          |
+-------+-------+------------+----------+----------+----------------+
| S     | Pos   | 870        | 0-1000   | 10 nA -- | 0.1% of F.S.   |
| trips | itive |            |          | 10 mA    | V\             |
|       |       |            |          |          | 0.02% of I     |
|       |       |            |          |          | range          |
+-------+-------+------------+----------+----------+----------------+
| S     | Pos   | 3700       | \~       | 0-10 A   | 0.5% of F.S.   |
| traws | itive |            | 0-2200   |          | V\             |
|       |       |            |          |          | 1% of I        |
+-------+-------+------------+----------+----------+----------------+
| RICH  | Neg   | 286        | 15       | 0-100 nA | 0.1% of F.S.   |
|       | ative |            | kV-22 kV |          | V, 1% of I     |
|       |       | 143        |          | 0-100 nA |                |
|       | Nega  |            | 10       |          | 0.1% of F.S.   |
|       | tive\ | 143        | kV-17 kV | 0-10 A   | V, 1% of I     |
|       | Pos   |            |          |          |                |
|       | itive |            | 0-100    |          | 0.1% of F.S.   |
|       |       |            |          |          | V, 10% of I    |
+-------+-------+------------+----------+----------+----------------+
| EM    | Neg   | 230        | 0-400    | 0-10 mA  | 0.02% of F.S.  |
| Cal.  | ative |            |          |          | V, 0.1% of I   |
|       |       | 230        | 0-600    | 0-2 mA   |                |
|       | Neg   |            |          |          | 0.02% of F.S.  |
|       | ative | 230        | 0-800    | 0-0.5 mA | V, 0.1% of I   |
|       |       |            |          |          |                |
|       | Neg   | 690        | 0-1000   | 0-0.1 mA | 0.01% of F.S.  |
|       | ative |            |          |          | V, 0.1% of I   |
|       |       |            |          |          |                |
|       | Neg   |            |          |          | 0.01% of F.S.  |
|       | ative |            |          |          | V, 0.1% of I   |
+-------+-------+------------+----------+----------+----------------+
| Muon  | Pos   | 2496       | \~       | 0-12 A   | 1% of F.S. V\  |
| Cha   | itive |            | 0-2000   |          | 1% of I        |
| mbers |       |            |          |          |                |
+-------+-------+------------+----------+----------+----------------+

Table 1: Summary of BTeV High Voltage Requirements.

# Requirements Common to all Detector Subsystems

## Setting and read back

All BTeV high voltages must be controllable by setting the voltage of an
individual channel or group of channels. The detector system grounds
must be defined locally at the detectors that are being powered. This
implies that the high-voltage power supplies must 'float' with respect
to their local ground. The current must be limited to a maximum value,
settable for an individual channel or a group of channels within a
module. Both voltage applied and current drawn must be monitored for
every channel.

-   **Requirement 2.1-1:** Each high voltage channel must have computer
    control of the following. Having 'computer control' means being
    controlled and monitored using a standard protocol and physical
    layer (*e.g.,* Ethernet, CAN):

    -   Output voltage settable to 0.1% of the maximum rated voltage.

    -   The output voltage value must be computer readable (See next to
        last bullet for set value readback requirements).

    -   Output current limit settable to 5% of the maximum rated current
        for the operating range.

    -   The output current value must be computer readable.

    -   The recovery from overcurrent must be manually re-settable by
        either a local panel control button or remotely by a computer
        command.

        Note: Automatic recovery when the fault is removed may also be
        required. Vendor should indicate additional estimated costs, if
        any, if this feature is provided.

    -   Output voltage over-limit and under-limit thresholds must be
        settable to 5% of the set point voltage.

    -   The recovery from overvoltage must be manually re-settable by
        either a local panel control button or remotely by a computer
        command.

        Note: Automatic recovery when the fault is removed may also be
        required. Vendor should indicate additional estimated costs, if
        any, if this feature is provided.

    -   Output must have on/off control and must be
        computer-controllable and monitored. There must be local on/off
        control (see Section 2.9).

    -   Any set point fault must send an "alarm" message to the control
        computer. A visual and/or audio alarm is also desirable.

    -   All computer settable controls (registers) must be computer
        readable.

    -   An computer-readable identification method for all different
        types of plug in units and any calibration constants is
        required.

-   **Requirement 2.1-2:** Each high-voltage power supply output must be
    able to have its current limit trip point remotely settable and
    monitored (computer-controlled). A manual test of this limit is also
    allowed in addition to the computer test.

    Note: This requirement might be eliminated if cost estimates to
    implement are too high.

-   **Requirement 2.1-3:** Each high-voltage power supply output must be
    able to have its overvoltage and undervoltage limit trip points
    remotely settable and monitored (computer-controlled). A local and
    manual test of these limits is also allowed in addition to the
    computer tests.

-   **Requirement 2.1-4:** The absolute accuracy of the
    computer-controlled settings for output high voltages may be only 1%
    (or better). The system must be able to be externally and remotely
    calibrated to the accuracies required in this document and be stable
    within the required tolerances for a minimum of eight hours over the
    specified operating range.

## Input and Environment

-   **Requirement 2.2-1:** The supplies must meet all specifications
    stated over an ambient operating temperature range of 10 ºC to 40
    ºC.

-   **Observation 2.2-1:** It is preferred that the supplies must
    operate with a nominal 120 VAC, single phase, 60 Hz input. The
    supplies must meet the specifications stated over an input voltage
    range of 105 VAC to 135 VAC, and a frequency variation of 55 Hz to
    65 Hz. 208 VAC operation may be acceptable if 120 VAC operation is
    not normally available with the vendor's products.

-   **Requirement 2.2-2:** The supplies must comply with MIL-STD-461B
    (similar to CE03 specification) for conducted and radiated
    emissions.

-   **Requirement 2.2-3:** The modules must comply with the ESD
    requirements IEC 60297-5-103 (IEEE 1101.10) and EN 61000-4-2.

## Output Characteristics & Connectors

The details of the output voltage and currents ranges are given for each
subsystem in Section 3. Only the general features are called out in this
section.

-   **Requirement 2.3-1:** The output voltages must "float" so that
    ground is defined at the load. This requirement has safety issues
    associated with it that are discussed in Section 2.8.

    Note: The term "float" implies high-impedance to ground relative to
    frequencies from DC to low multiples of 60Hz. It is desirable that
    the manufacture provide appropriate testing data if available.

-   **Requirement 2.3-2:** The output connectors shall meet safety code
    as described in FNAL Occupational Health and Safety Document,
    Chapter 5045: *High Voltage Coaxial Connectors,* Rev. 1/99. This
    document is available at:
    http://www-esh.fnal.gov/FESHM/5000/5045.html.

-   **Requirement 2.3-3:** All output connectors of lower-voltage
    supplies must be identical and type-keyed as to their output voltage
    if possible. All output connectors of higher-voltage supplies must
    also be identical and type-keyed as to their output voltage if
    possible.

    Note: An SHV connector may be chosen for all lower-voltage supplies.
    These are BNC-sized connectors and may prohibit denser packaging of
    supplies. Another reliable and safe connector may be chosen for
    lower-voltage supplies if this is the case. Type-keyed connectors,
    if available, are preferred.

-   **Requirement 2.3-4:** On turn-on and turn-off, the ramp rate of
    each output voltage from off to full on and on to full off,
    respectively, must be limited to several hundreds of milliseconds
    minimum.

    Note: This requirement might be eliminated if cost estimates to
    implement are too high.

-   **Requirement 2.3.5:** The peak-to-peak ripple of all outputs must
    be such that no measurable noise is introduced for the systems
    described in Section 3.

    Note: Fermilab will test prototype high-voltage power supply modules
    provided by the vendor to assure that this requirement is met.

-   **Requirement 2.3-6:** The long-term (eight hours minimum) stability
    must be such that intervention is not required to maintain preset
    voltage and current levels.

-   **Requirement 2.3-7:** The impedance of each high-voltage output
    shall be such that when deactivated, the output capacitors see
    sufficient impedance in which to discharge such that significant
    current spikes are eliminated.

## Cable Lengths & Remote Sense

The high-voltage power supplies will most probably be located in an area
outside the collision hall and consequently not in a radiation
environment. There is a possibility they will be located in the BTeV
collision hall. If so, it is understood that high-voltage components
tend to fail in high neutron environments. Section 2.5 gives expected
radiation levels in the collision hall where the power supplies would be
located if in the collision hall. If the power supplies are located in
the collision hall, the cables that distribute voltage to the detectors
will be relatively short (15 meters or less). If the power supplies are
located in the counting room, the cables that distribute voltages to the
detector will be relatively long (80 meters). At least one of the
following two requirements must be satisfied:

-   **Requirement 2.4-1a:** If the power supplies are located out of the
    collision hall, they must operate with output cables up to 80 meters
    in length.

-   **Requirement 2.4-1b:** If the power supplies are located in the
    collision hall they must operate with output cables up to 15 meters
    in length. If this condition exists, then Section 2.5 requirements
    must be met.

-   **Observation 2.4-1:** If necessary, the high voltage system may
    operate with remote sense cables. Some issues with safety may need
    to be addressed (see Section 2.8).

## Radiation Tolerance

Supplies that operate in the collision hall must be sufficiently
radiation tolerant so that their performance will not be significantly
degraded after ten years of running at the highest anticipated
luminosity. It may be possible to relax the radiation tolerance
requirement by approximately a factor of ten by judicious placement of
the supplies and/or the use of shielding.

-   **Requirement 2.5-1:** The high voltage system operating properties
    must not be degraded by the exposure (over 10 years) to 10 kRad of
    ionizing particles and a total fluence of 2 x 10^12^/cm^2^ of low
    energy (\< 14 MeV) neutrons. Degradation is defined here as
    something that no longer lets the system meet all the specification
    contained in this document.

## Packaging

The system must mount in standard racks to that they can share rack
space with other electronics.

-   **Requirement 2.6-1:** The unit must be packaged in a subrack base
    unit that mounts in standard 19 inch EIA racks.

-   **Observation 2.6.1:** The base subrack may contain the AC power
    input, computer monitor interface, and general system safety
    components. Plug-in units for these functions may also be used.
    Mean-Time-To-Repair (MTTR) might be reduced if plug-in units are
    used.

-   **Requirement 2.6-2:** The system must be a modular design with the
    high-voltage plug-in units into the base subrack. The number of
    channels must be maximized on the subrack level. A desirable minimum
    number of outputs per subrack is 128. In the case of 10 kV and
    higher units, this number may be less because of high-voltage
    distance clearance issues.

A desirable feature of the system would be to have different output
voltage modules plug into a common base subrack. This could make a more
efficient use of rack space and reduce the number of spare subracks that
are required.

## Maintainability

During data taking, maintenance downtime must be minimized.

-   **Requirement 2.7-1:** The system must be designed so that the MTBF
    (Mean Time Between Failures) of a module is 50,000 hours.

-   **Requirement 2.7-2:** The system must be designed so that the MTTR
    (Mean Time To Repair) is less than five minutes after the technician
    is at the location of the defective unit.

-   **Requirement 2.7-3:** If the fault is in a defective module (not
    the main subrack) the replacement must be accomplished without
    removing power from the entire subrack.

## Personnel Safety

Since the supply outputs will be referenced at the loads, it is
necessary that the system limit the extent that the output may float
with respect to local ground at the power supply. All "normal" personnel
safety standards must also be respected. Many of these safety issues are
discussed in Fermilab's ES&H Manual (FESHM; see 'Safety Manuals' at URL:
<http://www.fnal.gov/faw/fermilab_at_work.html>).

-   **Requirement 2.8-1:** The output ground potential must not exceed
    50 V when disconnected from the load ground.

-   **Requirement 2.8-2:** Since the output ground is floating, the
    output must protect personnel with a ground fault interrupt circuit.

    Note: The vendor should be prepared to describe his/her company's
    implemented method to assure personnel safety.

-   **Requirement 2.8-3:** The power supply, subrack and modules, must
    follow the guidelines described in Fermilab's ES&H Manual, Chapter
    5046 (FESHM5046) and the rules given in Chapter's 4 and 9 of the DOE
    Handbook of Electrical Safety.

    Note: The DOE Handbook of Electrical Safety can be accessed at URL:\
    <http://www-d0.fnal.gov/~hance/doe_esh.pdf>

-   **Requirement 2.8-4:** The modules must comply with the safety
    ground specifications in IEC 60950 (1991-10) and IEC 61140
    (1997-11).

## On/Off Control, Fault Monitoring & Safety Interlock Provisions

High-voltage power supplies connected, for example, to a single detector
plane are turned off in a potential or actual emergency situation both
quickly and at the same time. The high-voltage power supply module must
provide external safety interlocking of the high-voltage power supplies.

-   **Requirement 2.9-1:** Each module must provide external isolated
    input(s) to be used as an interlock to unconditionally prevent
    high-voltage outputs from being turned on, either manually or by
    computer control. This interlock must be fail safe (*e.g.* interlock
    cable break is a fault). The design of the interlock may impact hot
    swap and the vendor should discuss this possible conflict.

-   **Requirement 2.9-2:** Each module must provide one front-panel LED
    that indicates an internal or external fault condition initiated a
    disabling of one of its high-voltage outputs (*e.g.,* load
    overvoltage or overcurrent). The LED must be illuminated only when
    this disabling condition exists. Any safety interlock to this module
    must not illuminate the LED.

-   **Requirement 2.9-3:** Each type of failure mode must be able to be
    monitored by computer control. This includes information if the
    interlock caused the module's outputs to be disabled (see
    Requirement 2.9-1).

-   **Requirement 2.9-4:** Each module must provide an external isolated
    output that can be daisy-chained and that indicates an internal or
    external fault condition (*e.g.,* overcurrent, over temperature,
    *etc.*). This output must be able to be used directly as an input to
    disable the high-voltage outputs of the module or other modules.

# Requirements Unique to Each Subsystem {#requirements-unique-to-each-subsystem .unnumbered}

This section gives a brief description of each detector subsystem, and
lists requirements that are not common to all subsystems.

## Pixel Detector

The silicon pixel vertex detector is located in a vacuum vessel mounted
inside the BTeV dipole spectrometer magnet. The pixel sensors are
arranged in planes roughly perpendicular to the path of the proton and
antiproton beams. Each plane is made up of a number of modules rather
like a tile roof is constructed using shingles. The pixel sensor modules
are reverse biased silicon high voltage diodes. Before exposure to
radiation, the diode leakage current, which is supplied by the high
voltage supply, is very low. For sensor modules very close to the
circulating beams, exposure to ionizing particles will significantly
change the sensor properties during the life of the detector. As the
sensors become radiation damaged, it will be necessary to increase the
applied high voltage, and the leakage current will increase by many
orders of magnitude. While it is unclear how many modules may be biased
with a single high voltage channel, the modules closest to the beam
certainly will not share with any others.

-   **Requirement 3.1-1:** The supply must produce a negative voltage
    that is adjustable over the range of 0 V to 1000 V. The computer
    monitor must be accurate to 0.1% of full scale.

-   **Requirement 3.1-2:** Ripple and noise must be less than 0.1%, peak
    to peak, of the output over a frequency range of 20 Hz to 20 MHz.

-   **Requirement 3.1-3:** Stability of the output voltage (after 30
    minute warm up) over an eight-hour period of less than 0.1% from
    0 to 40º C.

-   **Observation 3.1-1:** The current may be adjusted in three ranges:
    10 nA to 1 µA, 400 nA to 100 µA, and 40 µA to 10 mA.

-   **Requirement 3.1-4:** The current monitor resolution must be 0.1%
    of the range setting.

It is not yet determined what, if any, electromagnetic shield will be
located between the pixel sensors and the circulating beams. If there is
not sufficient shielding, the circulating beams will induce currents in
the metal traces or wires carrying high voltage and ground to the
sensors. The particle beams are not DC, but bunched, with bunch length
of \~ 75 cm. The induced currents will represent a common mode noise
source that will have very high frequency components.

-   **Requirement 3.1-5:** The manufacturer must provide an alternate
    quotation for high voltage units listed above that have a
    peak-to-peak common mode voltage of less than 10 V and a frequency
    spectrum of \~0 to 100 MHz between the unit output and the load.

## Silicon Strip Detector

Silicon strip detectors (SSD's) will be employed as part of the forward
tracking system. These detectors are reverse biased high voltage diodes
similar to the pixel vertex detector sensors. From the point of view of
the high voltage system, the biggest difference between the pixel system
and the SSD system is that the SSD's will use positive high voltage and
the pixel system will use negative high voltage. Like the pixel system,
each SSD "station" will be composed of a number of separate modules.
Once again, modules closer to the beam will radiation damage faster than
modules further away from the beam. Consequently, while it may be
possible for a number of modules to be biased by a single high-voltage
channel, it will be necessary to have more than one high voltage per
station.

-   **Requirement 3.2-1:** The supply must produce a positive voltage
    that is adjustable over the range of 0 V to 1000 V. The computer
    monitor must be accurate to 0.1% of full scale.

-   **Requirement 3.2-2:** Ripple {unknown at this time}

-   **Requirement 3.2-3:** Stability {unknown at this time}

-   **Observation 3.2-1:** The current may be adjusted in three ranges:
    40 nA to 4 µA, 2 µA to 200 µA, and 100 µA to 10 mA.

-   **Requirement 3.2-4:** The current monitor resolution must be 0.1%
    of the range setting.

## Straw Detector

Straw tube drift chambers will be employed as part of the forward
tracking system. These are segmented multiwire proportional chambers.
Each straw tube contains a small diameter sense wire, which is held in
the center of the tube. The straw is metalized and will be connected to
a "ground" voltage that will be defined by the straw tube analog
front-end electronics. The sense wire will be connected to positive high
voltage. A blocking capacitor will allow the front-end electronics to
operate at low voltage with respect to local ground. High voltage will
be distributed to the sense wires by the same printed circuit board that
holds the front-end electronics. Each printed circuit board is expected
to service 32 straws. The baseline BTeV design calls for the use of only
one straw tube diameter, but it is possible that this design will be
changed, and two or three different diameter straw tubes will be
employed. In principal, all straw tubes channels with the same diameter
straws will be able to operate at a single high voltage. In practice, it
is likely that it will be desirable to bias straws very close to the
beam using a separate high voltage channel. The maximum number of high
voltage channels quoted here and in Table 1 corresponds to biasing each
group of 32 straw tube channels with a separate high voltage channel.

-   **Requirement 3.3-1:** The supply must produce a positive voltage
    that is adjustable over the range of \~ 0 V (supply may be a hundred
    volts or so from zero) to 2200 V. The computer monitor must be
    accurate to 0.5% of full scale.

-   **Requirement 3.3-2:** Ripple {unknown at this time}

-   **Requirement 3.3-3:** Stability {unknown at this time}

-   **Requirement 3.3-4:** The current must be adjusted to 1% in the
    range of 0 to 10 µA.

-   **Requirement 3.3-5:** The current monitor resolution must be 1% of
    full scale.

## RICH Detector

There will be two Ring Imaging Čerenkov Counters, one in each arm of the
BTeV spectrometer. High-energy charged particles emit light in the
Čerenkov radiator materials at an angle with respect to the particle
flight direction that is determined by the particle velocity. The
Čerenkov angle can be measured for each particle by focusing the light
onto an image plane where the photons fall on a ring image, the radius
of which is a simple function of the Čerenkov angle, and thus the
particle velocity. The measurement of the particle velocity, coupled
with the momentum measurement provided by the forward tracking system,
allows charged particles to be identified by type (mass). The BTeV
baseline design calls for the Čerenkov photons to be detected using
"Hybrid Photon Detectors" (HPDs). These are vacuum tubes in which
photoelectrons produced by interactions of incident photons in a
photocathode on the inside face of a clear vacuum window are accelerated
through a 20,000 V potential and detected by a silicon pad detector,
which is also located inside the vacuum tube. The baseline design calls
for 2080 HPDs, multiplexed in groups of 15. Each HPD requires three
negative high voltages (two for focusing electrodes): 20,000 V, 19890 V,
and 15830 V. In addition, the silicon pad detector located in each HPD
requires a positive bias voltage of 60 V.

-   **Requirement 3.4-1a:** The Type A supply must produce a negative
    voltage that is adjustable over the range of 15,000 V to 22,000 V.
    The computer monitor must be accurate to 0.1% of full scale.

-   **Requirement 3.4-1b:** The Type B supply must produce a negative
    voltage that is adjustable over the range of 10,000 V to 17000 V.
    The computer monitor must be accurate to 0.1% of full scale.

-   **Requirement 3.4-1c:** The type C supply must produce a positive
    voltage that is adjustable over the range of 0 V to 100 V. The
    computer monitor must be accurate to 0.1% of full scale.

-   **Requirement 3.4-2:** Ripple {unknown at this time}

-   **Requirement 3.4-3:** Stability {unknown at this time}

-   **Requirement 3.4-4:** The module must have a Reynolds Industries
    P/N167-3517 or equivalent connector for the output high voltage for
    17 kV or higher. Any safe connector may be used for the 100V unit.

-   **Requirement 3.4-5:** The current must be adjusted to 5% in the
    range of 0 to 100 nA for the 17 KV or higher units. The 100 V units
    must have a current range of 0 to 10 µA.

-   **Requirement 3.4-6:** The current monitor resolution must be 1% of
    the range setting for the high voltage units and 10% for the 100 V
    units.

## EM Calorimeter Detector

There will be two electromagnetic calorimeters, one in each arm of the
BTeV spectrometer. The active elements of the calorimeters will be light
producing lead tungstate (PbWO~4~) crystals. For incident electrons or
photons, the amount of light produced is directly proportional to the
photon or electron energy. Each crystal will be instrumented with a
photomultiplier tube. Since the light output of PbWO~4~ is a strong
function of temperature, the photomultiplier tubes will not be biased
using conventional bases, which use standing current in a chain of
resistors to generate different voltages for the dynode stages of the
tubes. Rather, each tube will be directly provided 4 ‑ 6 different high
voltages. Six voltages will be required if each dynode stage is biased
separately. It may be desirable to bias the first few (low current, high
voltage) stages using a conventional resistor chain, in which case only
four voltages will be required. Each calorimeter will contain 11,500
crystals and 11,500 photomultiplier tubes. Groups of 100 tubes will be
biased by a single group of high voltage channels.

Most of the BTeV detector elements are rather insensitive to the exact
value of the applied high voltage. The EM Calorimeter photomultiplier
tubes however, are very sensitive to the high voltage. The magnitude of
the photomultiplier signal is proportional to the amount of light
produced in the crystal, but depends exponentially on the applied high
voltage. In order to monitor sources of gain drift, it is important to
monitor the applied high voltage values with good precision.

-   **Requirement 3.5-1a:** The Type A supply must produce a negative
    voltage that is adjustable over the range of 0 V to 400 V. The
    computer monitor must be accurate to 0.02% of full scale.

-   **Requirement 3.5-1b:** The Type B supply must produce a negative
    voltage that is adjustable over the range of \~0 V to 600 V. The
    computer monitor must be accurate to 0.02% of full scale.

-   **Requirement 3.5-1c:** The type C supply must produce a positive
    voltage that is adjustable over the range of 0 V to 800 V. The
    computer monitor must be accurate to 0.01% of full scale.

-   **Requirement 3.5-1d:** The type D supply must produce a positive
    voltage that is adjustable over the range of 0 V to 1000 V. The
    computer monitor must be accurate to 0.01% of full scale.

-   **Requirement 3.5-2:** The peak-to-peak ripple must be less than
    100 mV.

-   **Requirement 3.5-3:** The output must be stable to 0.2 V over a
    24-hour period.

-   **Requirement 3.5-4:** The current must be adjusted to 0.1% in the
    range. The following maximum currents are required: 10 mA for the
    400 V units, 2 mA for the 600 V units, 0.5 mA for the 800 V units,
    and 0.1 mA for the 1000 V units.

-   **Requirement 3.5-5:** The current monitor resolution must be 0.1%
    of the range for all units.

-   **Requirement 3.5-5:** The current monitor resolution must be 0.1%
    of the range for all units.

## Muon Chambers Detector

Muon identification will be provided in the BTeV spectrometer by two
systems of proportional wire chambers and solid iron torroid magnets.
The chambers will be electrically similar to the straw tube chambers,
but instead of lightweight straws, the tubes will be 3/8 inch diameter
stainless steel. The system will contain 2304, 32-channel "planks," each
serviced by a 32-channel front-end electronics card, which will also
distribute high voltage. Since all of the muon tubes will be the same
size, it may be possible to bias a large number of planks with a single
high voltage channel.

-   **Requirement 3.6-1:** The supply must produce a positive voltage
    that is adjustable over the range of \~0 V (supply may be a hundred
    volts or so from zero) to 2000 V. The computer monitor must be
    accurate to 0.1% of full scale.

-   **Requirement 3.6-2:** Ripple {unknown at this time}

-   **Requirement 3.6-3:** Stability {unknown at this time}

-   **Requirement 3.6-4:** The current must be adjusted to 1% in the
    range of 0 to 12 µA.

-   **Requirement 3.6-5:** The current monitor resolution must be 1% of
    the range setting.