# US CMS {#us-cms .unnumbered}

**Parameters Book**

## Technical Description of the Baseline {#technical-description-of-the-baseline .unnumbered}

**Subsystems of the US CMS Project**

**December, 1998**

![](media/image1.png)

**1.0 Introduction**

The US CMS project was baselined in a review by DOE and NSF in May of
1998. That review concentrated on the cost and schedule of the
subsystems of US CMS. During that review a brief technical description
of the baseline scope of the project was submitted to DOE/NSF and was
subsequently put as an Appendix to the US CMS Project Management Plan.

An expanded definition of the technical baseline scope appears in the
Memorandum of Understanding between CERN and CMS. The deliverables are
defined to level 4 of the Work Breakdown Structure (WBS). The focus of
that document is on the estimated cost of those deliverables.

This document represents the next level of technical definition of the
subsystems of the US CMS Project. This technical description is
complementary to that given in the CMS MOU which is primarily fiscal.
Each subsystem of the WBS is defined and discussed in some detail in the
subsequent sections. A brief overview is given in this introduction.

The US CMS Collaboration has agreed to take leadership responsibility in
the CMS experiment for the endcap muon system, all the hadron
calorimetry, and associated aspects of the trigger and data acquisition
system. The Collaboration also plans to contribute to important areas of
the electromagnetic calorimetry, tracking, and common projects. The
general layout of the CMS Detector is shown in Figure 1.

A summary description of the US CMS baseline scope is provided below.
The details at the lowest work breakdown structure level are available
in the US CMS work breakdown structure dictionary dated May 19, 1998.
Level 2 WBS numbers associated with the various subdetector or
subsystems efforts are identified in Figure 1.

![](media/image2.wmf)

1.  Endcap Muon -- cathode strip chambers

2.  Hadron Calorimeter -- full HB, HOB, He, and HF transducers and
    readout -- HE scint, HF QP fibers

3.  Endcap Muon and Calorimeter Trigger. DAQ filter

4.  Electromagnetic Calorimeter -- barrel transducers, front end
    electronics, and laser monitor

5.  Forward Pixels

6.  Common Projects -- endcap yoke and barrel cryostat

7.  Project Office

Figure 1

**WBS 1.1 -- Endcap Muon System (EMU):**

![](media/image3.wmf){width="5.7659722222222225in"
height="4.186805555555556in"}

Figure 2

The CMS Endcap Muon System consists of three muon stations (four
stations are shown in Figure 2; the fourth station was eliminated as
part of the US CMS rescoping exercise) interleaved with three iron
disks. The angular region covered is 0.9 \< η \< 2.4. Here η is the
pseudorapidity, that is --ln\[tan(ϑ/2)\], where ϑ is the angle to the
beam axis. Muon stations are six-plane trapezoidal cathode strip
chambers. A precise coordinate measurement in cathode strip chambers
comes from interpolating charges induced by cathode strips.

The total number of chambers in the endcap system for the US CMS
baseline is 360 (372), where the number in parentheses includes spares.
The largest cathode strip chambers are 3.4 x 1.5 m^2^ in size. Each
chamber consists of six trapezoidal planes. Strips run radially to
provide a precise measurement of the φ coordinate, while wires run
azimuthally and define the radial coordinate of the track. The overall
area covered by the chambers is more than 950 m^2^ and the total number
of wires exceeds 1.7 million.

The US will manufacture, instrument, and install 148 large chambers, and
will make parts kits for the assembly of 148 smaller chambers by China,
and 76 smaller chambers by Russia. The US is responsible for all parts,
critical tooling, the on-chamber electronics, and the level 1 trigger.

There are 5 types of chambers shown schematically in Figure 3.

![](media/image4.wmf){width="5.7659722222222225in"
height="2.7888888888888888in"}

ME23/2 -- largest chambers, 10-degree in φ, outer ring of stations 2, 3

ME2/1 - inner ring of station 2, 20-degrees in φ

ME3/1 - inner ring of station 3, 20-degrees in φ

ME1/2 - intermediate ring of station 1, 10-degrees in φ (high resolution

CSC)

ME1/3 - outer ring of station 1, 10-degrees in φ

Figure 3

The ME23/2 are entirely the responsibility of the US.

For ME234/1 the US provides parts and critical assembly tooling. PNPI
(Russia) is responsible for assembly, testing, shipping, and
commissioning. For ME1/23 the US provides parts and critical assembly
tooling. IHEP (China) is responsible for assembly, testing, shipping,
and commissioning.

**WBS 1.2 -- Hadron Calorimeter (HCAL):**

![](media/image5.wmf)

Figure 4

The hadron calorimeter, shown schematically in Figure 4, in CMS is
organized geographically. There are five mechanically distinct
structures: the barrel (HB, 0. \< η \< 1.3), 2 endcaps (HE, 1.3 \<η \<
3), and the 2 forward (HF, 3 \< η \< 5) calorimeters. The US CMS hadron
calorimeter group responsibilities are to produce the barrel absorber
and the barrel scintillator tile/wave length shifter optics. In HF the
US will supply none of the absorber, but a fraction of the quartz fiber
sampling medium. In addition, the US will produce the barrel, outer
barrel, endcap, and forward transducers and front end electronics.

The hadron calorimeter is organized into towers of size ∆η∆φ = 0.087 x
0.087 for the barrel and endcap and ∆η∆φ = 0.174 x 0.174 for the forward
calorimeter. There are 3 longitudinal depth segments H1, H2, and HO in
HB. In HE there are two depth segments, while HF has three; HFE, HFH,
and HFT.

The work breakdown structure 1.2 items include all the effort to design,
produce, assemble, install, and commission the hadron calorimeter for
the CMS detector. The HB calorimeter is constructed of 36 wedges, each
weighing \~ 26 tonnes. The absorber is copper for HB and HE. The minimum
HCAL depth is 5.8 interaction lengths inside the CMS coil. The HE is
built as a single unit, but the optical system is packaged as 18
distinct 20-degree "pie" wedges, thus matching the HB segmentation.

There are distinct calorimeter towers in ∆η∆φ and in longitudinal depth.
These are supplied with electronics channels, which amplify and digitize
the signals produced by the HPD (HB, HOB, HE), and read out the PMT
(HF). The channel count (excluding spares) is 5184 in HB, 2160 in HOB,
3774 in HE, and 1728 (1920) in HF. The resulting digital signals are
stored in a pipeline and sent to the trigger/DAQ system by means of
multiplexed fiber optic communication systems. The received data is sent
to the trigger and DAQ systems separately. The system is calibrated
using LEDs, radioactive sources, and lasers.

**WBS 1.3 -- Trigger/Data Acquisition (TRIDAS):**

![](media/image6.png){width="5.7659722222222225in"
height="3.2069444444444444in"}

Figure 5

US CMS is responsible for elements of the first level muon trigger and
the level 1 calorimeter trigger. In addition, US CMS takes
responsibility for the data acquisition filter units (FU), and the event
manager (the layout of the data acquisition system is shown in Figure
5).

WBS element 1.3.1.1 includes all the effort to develop, produce,
assemble, install, and commission the Regional Muon Trigger. The system
is designed with 3 muon stations; however, the design allows easy
expansion to a 4-station system. The US will provide Port Cards (55),
Sector Receiver Cards (56), and Sector Processor cards (30) for the
level 1 CMS Muon Trigger.

Work breakdown structure element 1.3.1.2 includes all the effort to
develop, produce, assemble, install, and commission the Regional
Calorimeter Trigger. This system processes the electromagnetic and
hadronic trigger tower sums from the calorimeter front end electronics
and delivers regional information on electrons, photons, jets, and
partial energy sums to the global calorimeter level 1 trigger system.
The system begins after the data from the front end electronics is
received on optical fibers and translated to signals on copper and ends
with cables that transmit the results to the calorimeter global level 1
trigger system. The trigger is based on a 54 x 72 (η x φ) array of ECAL
and HCAL trigger towers. The towers supply 8 bits of energy information.
The US provides 22 VME crates with custom backplanes.

Work breakdown structure element 1.3.2 includes all the effort to
develop, produce, and assemble the parts of the CMS Data Acquisition
system for which the US CMS groups are responsible. The US has
undertaken the responsibility to provide the full Filter Unit system and
the complete Event Manager system. In the R&D phase, US groups will also
participate in the design and testing of prototyping modules that can be
used both on the Readout Units and the 432 Filter Units. The complete
DAQ system will perform at 75 kHz, and the system is scalable.

**WBS 1.4 -- Electromagnetic Calorimeter (ECAL):**

![](media/image7.wmf){width="5.763194444444444in"
height="2.4291666666666667in"}

Figure 6

US CMS is responsible for elements (identified in Figure 6) of the
electromagnetic calorimeter. This device utilizes PbWO~4~ crystals to
detect electromagnetic showers. The US is responsible for partial
procurement, 36000, of the light transducer Avalanche Photodiode (APD),
the floating point unit (FPU), 60200, which converts a voltage to a
digital number, the bit serializer which converts that number into a
serial bit stream for transmission off the detector, and elements of the
laser monitor/calibration system.

There are 61,200 crystals in the barrel ECAL, or EB. Each has a pair of
APDs with 25 mm^2^ sensitive area. The US is responsible for \~50% of
the APD prototypes and \~30% of the procurement of the production APDs.

The US is responsible for the design and procurement of all the EB
front-end multi-ranging floating point units (FPU), and CHFET
bit-serializers.

The US is responsible for elements of the laser monitor system. These
include the laser, cooling, collimators, shutters, mirrors, and other
optical mounts.

**WBS 1.5 -- Forward Pixel Tracking (FPIX):**

![](media/image8.wmf){width="5.764583333333333in"
height="3.357638888888889in"}

Figure 7

US CMS is responsible for the delivery of the forward silicon pixel
(FPIX) detector system. This system consists of 4 assemblies, or wheels,
(shown in Figure 7) of silicon pixels. These wheels are made from
subassemblies, which are arranged as "turbine blades". This unique
arrangement allows for Lorentz force charge sharing among pixels, thus
enabling the devices to have good impact point resolution in 2
dimensions.

The FPIX system covers the angular range 1.4 \< η \< 2.6. The US will
design, assemble, deliver, install, and commission the entire system.
This system consists of 4 disks containing 96 "blades". Each blade has 7
silicon sensor arrays comprising 45 readout chips. There are 4320 total
readout chips and 672 Si sensors. The total system has \~12 million
pixels, each 150 μm x 150 μm. The system consists of sensors, readout,
mechanical support, and ancillary services.

**WBS 1.6 -- Common Projects:**

Common Projects in CMS are the magnet and the common software and
computing. The US pays a representative share of the Common Projects as
defined to be a fixed fraction of the contribution of the US to CMS. The
US contribution will be defined to be the M&S items of the baseline
scope of the US CMS project. The fraction is currently assessed to be
31.5 percent. This currently agreed upon US contribution to Common
Projects is \$23M.

![](media/image9.wmf){width="5.704861111111111in" height="5.2in"}

Figure 8

The US CMS contribution is made by material acquisitions rather than by
cash payments. The two major efforts in US CMS are related to the US CMS
interests in the hadron calorimeter and the forward muon system. This
may evolve, as the cost experience with CMS Common Projects becomes
clearer (i.e., we may be able to provide more or less than currently
planned in the way of material acquisitions based on real cost
experience.)

The US takes full responsibility for the design and procurement of the
endcap steel yoke (shown as the yellow toroids in Figure 8 bottom). The
US also takes partial responsibility for the barrel yoke and the coil
vacuum tank (shown in Figure 8 Top). These two projects have already
been bid and the contract for the endcap will be awarded within a few
months. The contract for the barrel is already in place.

**WBS 1.7 -- Project Office:**

This work breakdown structure element includes all the effort needed to
exercise Project Management in CMS. The tasks include:

Baseline Development

The first phase of the US CMS Project is to construct a baseline cost
estimate, have it reviewed, and accepted by the DOE and NSF as an
acceptable estimate of the set of deliverables which can be supplied
with high confidence for the total funding available to the project.

Tracking

A major function of the US CMS project office is tracking the progress
of the project. That function includes the overall level 1 schedule, the
level 2 linked schedules, and the derived annual Statement of Work. The
actual costs are to be reported at the lowest work breakdown structure
level by means of invoices to the Fermilab general ledger.

Reporting

The US CMS project office will report to the Fermilab Project Management
Group, the DOE/NSF Project Manager, and the Joint Oversight Group in a
manner specified by those entities.

Northeastern University Administration

The NSF funds will be sent from NSF to Northeastern University. They
will be divided then as per instruction of the technical
director/construction project manager and sent to the NSF supported
groups of US CMS. In order to perform these functions, Northeastern
University requires the services of an Administrative Assistant.

Support for Education/Outreach

The education liaison function includes the development of educational
proposals of US CMS. In support of these and other educational
activities, the US CMS project office supplies funds for programmatic
travel and for M&S supplies.

1.  **Endcap Muon (EMU)**

##  {#section .unnumbered}

An overall view of the CMS Endcap Muon (EMU) system was shown in the
introduction. There are 432 endcap chambers of trapezoidal shape placed
between the iron disks, which return the magnetic flux of the central
solenoid and also shield the chambers. The chambers are arranged to form
three disks, called stations ME1, ME2, and ME3. The station ME1 has
three rings of chambers: ME1/1, ME1/2, and ME1/3, while the other three
stations are composed from two rings of chambers: ME2/1 and ME2/2, ME3/1
and ME3/2. All but the ME1/3 chambers overlap in ϕ. There are 18 or 36
chambers in every ring.

The performance requirements for the system of are as follows:

\- 75 µm off-line spatial resolution in ϕ for ME1/1 and ME1/2 chambers
and 150 µm for the others;

\- 1-2 mm resolution in ϕ at the Level-1 trigger;

\- 1-2 cm resolution in R both at Level-1 trigger and in off-line;

\- \>92% probability of identifying correct bunch crossings, occurring
at LHC every 25 ns;

\- reliable performance at 1 kHz/cm^2^ rates with no drastic aging
effects during the 10 years operation.

US responsibilities (deliverables) include:

-   Overall EMU project co-ordination and integration.

-   Design of ME1/2, ME1/3, ME2/1, ME2/2, ME3/1, ME3/2 chambers.
    Production of all parts for all these 360 (+12 spares) chambers: 72
    (+2) ME1/2, 72 (+2) ME1/3, 36 (+2) ME2/1, 72 (+2) ME2/2, 36 (+2)
    ME3/1, and 72 (+2) ME3/2.

-   Design and production of assembly tooling and testing equipment for
    three US sites: Fermilab, University of California (UC), and
    University of Florida (UF). Production of critical tooling and
    equipment for two foreign sites: PNPI (St.Petersburg) and IHEP
    (Beijing).

-   Assembly and complete system tests (chambers with all on-chamber
    electronics) of 72 (+2) ME2/2 and 72 (+2) ME3/2 chambers[^1].
    Installation and commissioning of these chambers at CERN.

-   Design and Production of all on-chamber DAQ and Level-1 Trigger
    electronics for all 360 chambers (plus 10% of spares).

-   Design and Production of services for the system of 360 chambers
    (High Voltage, Low Voltage, Electronics Cooling, and Local Gas
    Distribution Systems).

-   Design and Production of the Alignment System for the 360 chambers.

    1.  **Cathode Strip Chambers (WBS 1.1)**

**EMU Cathode Strip Chambers: general description and mechanical
parameters**

Endcap muon chambers are so-called Cathode Strip Chambers, or CSCs, of a
trapezoidal shape. Seven panels stacked together form six gas gaps, each
of which contains a plane of anode wires (positive high voltage is
applied to the wires). One of the two cathode surfaces in each of the
gaps is milled lengthwise to form a fan-shaped set of strips (each strip
has a constant ∆ϕ width). A charged particle passing through each of the
gaps makes an avalanche on a wire. By reading out a direct signal from
the wires and an induced signal from the strips one can localize the
track in both directions. Wires grouped in bunches provide a coarse
measurement of a radial coordinate, while an interpolation of charges
induced on strips provides a precise measurement of a ϕ-coordinate.
Small wire spacing allows for an efficient bunch crossing tagging. CSCs
have a few important features: they combine both the precision and
trigger functions in one device; can operate in high rates, in large and
non-uniform magnetic fields; do not require tight gas, temperature or
pressure control; and easily allow for a variety of strip patterns (e.g.
fan-shaped).

There are 5 different chamber types in the system with the total number
of chambers of 360 (plus 12 spares). The overall area covered by the
chambers is about 950 m^2^, and the total number of wires about 1.6
million. Table 1 summarizes all chamber parameters. The only difference
between different chamber types is their size, strip and wire channel
count, while the basic underlying design is identical.

*Table 1. Chamber parameters.*

  ---------------------- --------- --------- --------- ---------- -----------
                         ME1/2     ME1/3     ME2/1     ME3/1      ME23/2

  **Overall chamber                                               
  parameters**                                                    

  Number of chambers     72        72        36        36         144

  Additional spares      2         2         2         2          4

  Planes per chamber                         6                    

  ϕ-coverage, degrees    10°       10°       20°       20°        10°

  ϕ-overlap, \# strips   5         none      5         5          5

  η-coverage             1.2-1.6   0.9-1.1   1.6-2.4   1.75-2.4   Varies

  η-overlap                                  none                 

  Length, mm             1800      1900      2065      1845       3380

  Width (top), mm        1078      1192      1534      1534       1530

  Width (bottom), mm     740       859       751       835        895

  Chamber thickness, mm                      250                  

  **Basic single plane                                            
  parameters**                                                    

  full gas gap (2h), mm                      9.5                  

  wire diameter, μm                          50                   

  wire spacing, mm       3.16      3.16      3.12      3.12       3.16

  **Width of dead area                                            
  along chamber edges**                                           

  width at the top, mm                       94                   

  width at the bottom,                       68                   
  mm                                                              

  width along long sides                     120                  
  , mm                                                            

  **Wires**                                                       

  wires per plane        528       560       620       550        1028

  wires per wire group   7-11      16,17     5, 6      5, 6       16

  wire group width, mm   22-35     51, 54    16, 19    16, 19     51

  wire group cap., pF    30-70     70-110    20-60     20-60      80-150

  wire groups per plane  64        32        112       96         64

  **Strips**                                                      

  ∆ϕ(single strip), mrad 2.33      2.16      4.65      4.65       2.33

  strip pitch (top), mm  10.4      14.9      15.6      15.6       16.0

  strip pitch (bottom),  6.6       11.1      6.8       7.8        8.5
  mm                                                              

  gap between strips, mm                     0.5                  

  strip capacitance, pF  110       145       145       130        250

  strips per plane       80        64        80        80         80

  **HV**                                                          

  Operating HV, kV                           4.1                  

  HV segments per plane  2         3         3         3          5
  ---------------------- --------- --------- --------- ---------- -----------

**EMU Cathode Strip Chambers: detailed design description**

The exploded schematic view of the chamber is shown in Fig.1. Seven 16
mm thick panels form the basis of the chamber mechanical structure. They
are made of 1.6 mm copper clad FR4 skins[^2] commercially glued on 3.2
mm cell size, 12.7 mm thick polycarbonate honeycomb core[^3]. The gap
bars are glued along the perimeter of each other panel and form six gas
gaps of 9.53 mm when all seven panels are stacked together. There are 2
to 4 buttons in each plane placed along the chamber center line and the
entire stack of panels is tighten down in these points. Thus, the panels
have no more than 60 cm of unsupported length. Measurements showed that
most of the panels are flat within required ±0.2 mm on such spans.

![](media/image10.wmf){width="5.133333333333334in"
height="4.129861111111111in"}

Fig. 1. An exploded view of a EMU Cathode Strip Chamber.

The panels also serve the role of cathodes. One side of six panels has a
pattern of 64 or 80 strips milled by a CNC machine. Strip pitch has
constant in azimuth coordinates and, thus, varies from the bottom to
the top of a chamber; also, it is different for different types of
chambers, the full range being from 6.6 to 16.0 mm. The gap between
strips is about 0.5 mm. Milling is done with a 45° cutter to make cut
edges smooth. The position of strip centers was measured to have a
spread of 32 µm (rms), and strip straightness\-\--20 µm.

A special machine has been designed to wind wires directly on panels.
Gold plated tungsten wires, 50 µm in diameter, are spaced by about 3.2
mm and stretched at 250 g tension (60% of the elastic limit). They have
maximum length of 1.2 m and run from end to end without any intermediate
supports. The wire tension does not deviate from the nominal by more
than ±5%, while wire spacing are within ±150 µm. After winding wires are
first glued and then soldered on an automated soldering machine. Groups
of contiguous wires are connected to make one readout channel. The wire
signals are read out via 1 nF blocking capacitors and HV is distributed
to wires at their other end (one fully controllable HV channel is
provided to each plane).

Each wire plane is sub-divided in 3-5 independent HV segments. In places
where buttons had to be inserted two wires are removed and on one of the
two panels forming the gas gap 3.2 mm thick and 16 mm wide FR4 strips
running along wires are glued. By virtue of charging up, they
substantially reduced electric field on the four wires stretching over
them. Thus formed boundary allows for independently turning HV on/off on
any of the five wire plane sections, should the need arise.

After stacking the panels and tightening perimeter bolts, continuous
beads of RTV are applied along perimeters of each of the planes. An
external frame formed by 3.2 mm thick Al side plates is attached along
the chamber perimeter. It stiffens the chamber and, also, interconnects
top and bottom copper skins to form a complete Faraday cage. Each
chamber has three mounting points, one at the middle of bottom side and
two in the corners at the top of the chamber.

######## **EMU Cathode Strip Chambers: High Voltage system**  {#emu-cathode-strip-chambers-high-voltage-system .unnumbered}

Each plane of the 360 chambers will have one computer controlled HV
channel (each channel is capable of providing current up to 200 A at
the maximum HV of 6 kV). The HV system will be based on a commercial
multi-channel HV main frame (CAEN, Model SY 527 with A-832P HV cards).

The all needed HV cards can be accommodated in 18 crates to be mounted
in the control room. The outputs of the HV cards will be connected to
the fan-out terminals located on the outer rim of the endcap disks by
12-conductor flexible about 100 m long cables. Each terminal serves a
40 sector of a muon station. At the fan-out terminals each channel,
which corresponds to a single plane of one of the CSC chambers, is
fanned out into 3-5 chamber HV segments. At these easily accessible
fan-out terminals it is possible to disconnect manually any of the
segments of a single plane if that segment is drawing excessive current
(current monitoring for each of the segments will be available at the
fan-out terminals). Several multi-conductor cables (depending on chamber
size) connect the fan-out terminal to each chamber. Table 2 summarizes
the number of different elements in the CSC HV system.

Table 2. Elements of the CSC HV system.

  -------------------------------------------------------- -------- --------
                                                           needed   spares

  Independently computer controlled HV channels (one per   2,160    
  CSC plane)                                                        

  Total number of chamber HV segments                      8,208    

  HV cards (12 channels per card)                          180      8

  HV crates (10 cards per crate)                           18       2

  100 m long 12-lead HV cables                             180      6

  HV fan-out terminals (1 per 40 sector of each station)  54       4
  with local HV cables                                              
  -------------------------------------------------------- -------- --------

######## **EMU Cathode Strip Chambers: Deliverables** {#emu-cathode-strip-chambers-deliverables .unnumbered}

This section summarizes in explicit form all deliverables associated
with EMU CSC sub-project.

**WBS 1.1.1.1 CSC and Tooling: R&D, Design, and Tests**

-   complete design and prototyping of all five types of chambers
    (ME1/2, ME1/3, ME2/1, ME3/1, ME23/2);

-   development of the chamber assembly procedures; design and
    prototyping of the assembly tooling;

-   chamber tests not associated with the chamber production per se
    (e.g., tests of prototypes in cosmic rays and in the beam, chamber
    aging tests, gas optimization studies, etc.)

**WBS 1.1.1.2 Overall CSC Production Management**

-   the chief chamber production engineer,

-   the chamber cost and schedule engineer,

-   miscellaneous expenses associated with management and technical
    coordination of chamber production spread over three US and two
    foreign sites.

####### **WBS 1.1.1.3 Fermilab Site Task**

-   procurement of all materials for all 360 (+12 spares) chambers;

-   setting up facilities with appropriate dedicated tooling for panel
    production;

-   panel production for all 360 (+12 spares) chambers;

-   setting up facilities with appropriate dedicated tooling for chamber
    assembly;

-   assembly of 72 (+2) ME2/2 and 72 (+2) ME3/2 chambers;

-   crating and shipping of the assembled chambers to UC and UF sites;

-   procurement of the critical tooling for the two foreign sites, PNPI
    and IHEP;

-   shipping of 72 (+2) ME1/2 and 72 (+2) ME1/3 chamber assembly kits to
    IHEP;

-   shipping of 36 (+2) ME2/1and 36 (+2) ME3/1chamber assembly kits to
    PNPI.

**WBS 1.1.1.4 UCLA Site Task**

-   setting up facilities with appropriate dedicated tooling and
    equipment for final chamber assembly and system tests;

-   long term high voltage training of 36 (+1) ME2/2 and 36 (+1) ME3/2
    chambers

-   final assembly of chambers with all on-chamber electronics and
    services

-   system performance tests of 36 (+1) ME2/2 and 36 (+1) ME3/2
    chambers; repairs if the test results do not meet specifications

-   shipping of the tested chambers to CERN

**WBS 1.1.1.5 UF Site Task**

-   setting up facilities with appropriate dedicated tooling and
    equipment for final chamber assembly and system tests;

-   long term high voltage training of 36 (+1) ME2/2 and 36 (+1) ME3/2
    chambers

-   final assembly of chambers with all on-chamber electronics and
    services

-   system performance tests of 36 (+1) ME2/2 and 36 (+1) ME3/2
    chambers; repairs if the test results do not meet specifications

-   shipping of the tested chambers to CERN

**WBS 1.1.1.6 Installation and Commissioning**

-   installation and commissioning of 72 (+2) ME1/2 and 72 (+2) ME1/3
    chamber at CERN

**WBS 1.1.1.7 High Voltage system**

-   design and tests of the high voltage system for the entire system of
    360 chambers

-   procurement of 20 HV mainframes (CAEN Model SY 527) and 188 HV cards
    (CAEN A-832P).

-   procurement of 186 100 m long 12-lead HV cables with connectors

-   procurement of 58 HV fanout boxes with local HV distribution cables

-   commissioning of the HV system at CERN

**1.1.2 Front End Electronics**

The EMU front-end electronics system consists of four types of boards:
cathode front-end boards, anode front-end boards , DAQ Motherboard and
Trigger Motherboard. Depending on chamber types, there are typically 4
to 5 cathode front-end boards and 3 to 7 anode front-end boards per
chamber. Each cathode or anode front-end board serves 96 input channels.
There is one DAQ Motherboard and one Trigger Motherboard per chamber.
All the boards are mounted on the chamber. The motherboards serve as
links between the front-end boards and the rest of the experiment. They
send the readout and trigger data to the central DAQ and the Level-1
trigger systems. They receive trigger, timing and control (TTC) signals
and distribute them to the front-end boards. The following table shows
the scope of the system. The numbers of each type of boards in the EMU
system , including spares, are listed below in Table 3.

Table 3 Number of Boards for EMU Front-end Electronics

  ----------------------------------------- -----------------------------
  Cathode Front-end Board                   1901

  Anode Front-end Board                     1624

  DAQ Motherboard                           396

  Trigger Motherboard                       396
  ----------------------------------------- -----------------------------

**Cathode Front-end Boards (WBS 1.1.2.1)**

Each cathode front-end board receives 96 inputs and reads out a tower
consisting of 16 neighboring strips per layer by 6 layers deep. The
functional diagram for the cathode front-end board is shown in Figure 2.
The input signals from each of the strips are sent into 16-channel
charge-sensitive preamplifier-shaper ASIC\'s (There are 6 such ASIC\'s
per front-end board). Input signals are amplified and shaped into
voltage pulses. The output pulse shape corresponding to an impulse
charge input is semi-Gaussian and the peaking time is 100 ns . To
minimize pile-up effects in high rate situations, circuits to cancel the
long ion drift tail of a chamber pulse are incorporated into the shaper.
Channel-by-channel calibration will be done using a set of precisely
matched capacitors that couple a test pulse to each channel\'s input.

![](media/image11.png)Figure 2. Functional Diagram of the Cathode
Front-end Board.

One output of the shaper is connected to the trigger path whose main
components are a Comparator Network and a Local Charge Track (LCT)
processor. The comparator network locates the centroids of the induced
strip charges in each chamber layers to an accuracy of half the strip
width and marks its time. The resulting information is fed into the LCT
trigger processor which look for coincidence of cluster centroids from a
minimum number of chamber layers which form a \`\`road\". The time,
location and angle of the LCT are used to determine trigger primitive
parameters for the Level-1 muon trigger.

The other output of the shaper is connected to the DAQ readout path. The
voltage is sampled every 50 ns and held in a Switch Capacitor Array
(SCA) during the Level-1 latency. The stored voltage samples are
digitized and readout when 1) an associated LCT trigger occurs, and 2)
the LCT is time-correlated with a Level-1 Accept. Otherwise, the stored
samples are written over. This readout strategy significantly suppresses
random background hits induced by neutrons and photons. The digitized
data is saved in memory and transmitted to the main DAQ system upon
request by the MB. The following table lists the number and types of
IC\'s housed on the cathode front-end board.

+-------------------------+----------------------+--------------------+
| **ASIC Type**           | **No. Channels per   | ## No. of          |
|                         | ASIC**               |  ASIC\'s on board  |
|                         |                      | {#no.-of-asics-on- |
|                         |                      | board .unnumbered} |
+-------------------------+----------------------+--------------------+
| Preamp-Shaper           | 16                   | 6                  |
+-------------------------+----------------------+--------------------+
| SCA                     | 16                   | 6                  |
+-------------------------+----------------------+--------------------+
| Readout Control (FPGA)  | 96                   | 1                  |
+-------------------------+----------------------+--------------------+
| Comparator              | 16                   | 6                  |
+-------------------------+----------------------+--------------------+
| LCT Demux/Controller    | 96                   | 2                  |
+-------------------------+----------------------+--------------------+
| LCT Selector            | 96                   | 2                  |
+-------------------------+----------------------+--------------------+
| Trigger RAM (32 kByte)  | 6                    | 16                 |
+-------------------------+----------------------+--------------------+
| ADC (12 bits, 20 MHz)   | 1                    | 6                  |
+-------------------------+----------------------+--------------------+

#### Table 4 IC\'s on the Cathode Front-end Board {#table-4-ics-on-the-cathode-front-end-board .unnumbered}

**Anode Front-end Boards (WBS 1.1.2.2)**

![](media/image12.png){width="3.775in" height="2.0166666666666666in"}The
anode readout is similar to that of the cathode except that the emphasis
is on the accuracy of timing instead of pulse height. Each input channel
of the anode front-end board is a ganged group of wires (10 to 20) in a
chamber layer. Figure 3 shows the functional diagram for the anode
front-end board.

Figure 3. Functional Diagram of the Anode Front-end Board

The input signals go into 16-channel preamplifier-shaper ASIC\'s (6 per
board). The amplifiers are similar to the ones on the cathode front-end
board, but optimized for the summed anode input capacitance. The signals
are shaped with shaper peaking time of 30ns and sent into
discriminators. The output pulses from the discriminators are used to
form the LCT and to determine the bunch crossing time of the track
segment. They are also latched and pipelined for readout into the DAQ
network via the motherboard, providing hit/no-hit information for each
of the wire groups. Table 5 lists the IC\'s housed on the anode
front-end board.

+------------------------+---------------------+-----------------------+
| **ASIC Type**          | **No. Channels per  | ##                    |
|                        | ASIC**              |  No. of ASIC\'s on bo |
|                        |                     | ard {#no.-of-asics-on |
|                        |                     | -board-1 .unnumbered} |
+------------------------+---------------------+-----------------------+
| Preamp-Shaper          | 16                  | 6                     |
+------------------------+---------------------+-----------------------+
| Discriminator          | 16                  | 6                     |
+------------------------+---------------------+-----------------------+
| Readout Control (FPGA) | 96                  | 1                     |
+------------------------+---------------------+-----------------------+
| LCT                    | 96                  | 2                     |
| Pretrigger/Controller  |                     |                       |
+------------------------+---------------------+-----------------------+
| LCT Selector           | 96                  | 2                     |
+------------------------+---------------------+-----------------------+
| Trigger RAM (32 kByte) | 6                   | 16                    |
+------------------------+---------------------+-----------------------+

Table 5 IC\'s on the Anode Front-end Board

**The DAQ Motherboard (WBS 1.1.2.3)**

![](media/image13.png){width="4.3277777777777775in"
height="5.179861111111111in"}The Motherboards serve as links to the
level-1 muon trigger and to the central DAQ of CMS. There is one DAQ and
one Trigger motherboard for each CSC module. The functionality of the
trigger and DAQ Motherboards is shown in Figure 4.

Figure 4. Functional Diagram of the Readout Motherboard.

The readout of the data from each front-end board is coordinated by the
DAQ Motherboard. The digitization of the stored voltage samples on the
cathode front-end boards and latching of the hits on the anode front-end
boards are initiated by the arrival of a Level-1 accept which has a
bunch crossing number matching that of an LCT. When this occurs, the
readout controllers on the front-end boards are notified. Digitization
will begin on the cathode front-end boards. Those pulse samples stored
on each of the 96 channels on the front-end board within a time window
of 800 are digitized. The digitized data is sent to the output buffer on
the motherboard and transferred by optical link to the central DAQ.

The DAQ motherboard also acts as interface to the Run Control and to
Slow control. The interfaced functions include down-loading of the FPGA
and DSP programs, resetting of the readout controller on the front-end
board, down-loading calibration information, down-loading commands for
turning off bad channels, monitoring of low voltage levels and
temperature. JTAG will be used for the slow control.

**Trigger Motherboard (WBS 1.1.2.4)**

The information associated with LCT\'s generated on cathode front-end
boards and anode front-end boards are sent to the Trigger Motherboard.
This information includes the bunch crossing time and the location and
angle of each LCT. When the timing between a cathode LCT and an anode
LCT\'s is found to agree within +- 1 bunch crossing, the LCT is a valid
one. When more than one valid LCT is found for the chamber, only the
best two, as determined by quality factors, are retained and passed on
to the port cards along with the (anode) LCT bunch crossing number.
(Each port card spans a 30 degree sector of an endcap station.) The
tasks performed by the trigger motherboard are fully pipe-lined and
synchronous with the beam-crossing clock. Another function vital to the
operation of the front-end electronics, receiving and fan-out of TTC
signals to the front-end boards, is also located on the Trigger
Motherboard.

**Low Voltage Supply and Distribution System (WBS 1.1.2.5)**

The voltages required to operate the various types of the electronics
boards in the EMU system will be supplied by 2(3) main supplies, each
capable of generating up to 1125 A at 80 volts. The generated power will
be transmitted by copper conductors at 80 volts to each of the endcap
muon stations where it will be distributed to the electronics system
using DC-to-DC converters (960 units in total) which transform the
delivered power to the desired voltages.

3.  **Mechanical Structure**

The CSC chambers are mounted directly to the iron surface of the disks
using quasi-kinematic mounts In all stations except ME1/3 the chambers
are overlapped to provide full phi coverage. The quasi-kinematic mounts
are formed from Al extrusions and are bolted directly to the chamber
frames. These mounts are bolted onto wings mounted on posts bolted to
the iron disks. Fig. ?? shows how the chambers are attached to the
disks.

The quasi-kinematic mounts locate the CSC chambers and provide some
compliance for mechanical tolerances or thermal expansion. One mount,
RZ, fixes the location of the chamber tightly in all dimensions: , R,
and Z. Another mount, Z, has a slot which fixes the chambers in  and
Z, but not R. The third mount, Z, has alarge hole which does not
constrain the chambers in either or R, but does fix the Z location.

  ------------------------ -------------------- -------------------------
  item                     Number/chamber       Total number

  Disk posts               2                    720

  RZ mount bracket        1                    360

  Z mount bracket         1                    360

  Z mount bracket          1                    360
  ------------------------ -------------------- -------------------------

4.  **Cooling**

The front-end electronics is atttached to the face of the CSC chambers
as close as possible to the ends of the strips (cathodes) or wires
(anodes). The muon trigger electronics will be located around the
periphery of the iron disks in standard racks. All the electronics must
be cooled, but the rack-mounted electronics will be cooled by
conventional rack systems. The front-end boards must be cooled by a
special system attached to the chambers. Table 5 gives an estimate of
the heat loads for the front-end boards.

Table 5: Estimate of heat load for the largest chamber ME234/2.

  ----------------------- ---------------- -------------- -----------------
  electronic board        heat/board(w)    boards/cham    heat/chamber(w)

  cathode 96-channel FE   22               5              110

  anode 96-channel FE     11.0             4              44
  ----------------------- ---------------- -------------- -----------------

The estimated heat load for the entire CSC systems is 54KW (ME1/1
excluded). Table 1 shows an estimate of the heat load for the largest
chambers (ME2/2 and ME3/2). The most efficient method for removing this
heat is to mount each of the boards on a metallic pad which has thermal
contact with the heat production on the board. Then the pads are cooled
using a connection to a pressurized water system. The overall height of
the CMS detector is 14 m so the water pressure differential over this
height will vary by roughly 1.4bar. The return pressure should be higher
than this differential and the supply pressure should be at least 2bar
above the return.

On the outer face of the chamber copper pads are mounted under each
electronic board. All the pads on a chamber face are connected by a
"continuous" 1/4" copper tube which is brazed to each pad (see Fig. ??).
A flexible 1/4" hose is connected to the water inputs and outputs of
each chamber. This flexible hose connects to the manifold laterals via
O-ring fittings. An aluminum faraday shield (for both RF and cooling) is
mounted on each copper pad to cover the electronic board.

The present plan for stations 2 and 3 is to connect three chambers in
series (2 10-degree and 1 20-degree CSCs) covering a sector of 20
degrees as shown in Fig. 2. For station 1, which has no 20-degree
chambers, we will connect only two 10-degree chambers in series.

The cooling manifolds, supply and return, are located on the outer edge
of each disk. These manifolds are 1.25" stainless steel pipes with
lateral connections to each group of CSC chambers. Each face of the
12-sided endcap disks contains one section of the manifolds; sections
are connected by O-ring seals on flanged ends. In order to accommodate
installation tolerances we add a short flexible section for each
connection. Along the manifold holes are drilled for local connections
and 1/4" stainless steel half couplings are welded. Each lateral
connection has a 1/4" ball valve; the return connection also has a flow
restrictor (2.8l/m or .75GPM). Flexible 1/4" hoses carry the water to
the chambers. Each hose connection is made with O-ring fittings which
are robust and reliable.

Fig. 3 shows a close-up view of the water manifolds and the cable trays
on the outer edge of the endcap disk. A top view shows the layout of
lateral connections to either side of the disk. Also shown is a cut view
of the edge of the disk with manifolds for water, gas, and hydraulics.

The input water temperature will be 18-20 degrees C (about 5 degrees
above the dew point). The sizing of the system has been made to insure
that the temperature rise per connection remains less than 2 degrees C.

**1.1.5 Alignment System**

The endcap alignment system (for track matching and momentum measurement
) defines positions in the endcap relative to the Central Tracker and
Barrel muon systems by connecting to the Link-Barrel system. In order to
trigger on and define the correct position of passing particles (after
software alignment correction), mechanical chamber positions and
orientations need to be known with a reasonable tolerance, especially
the R coordinates and φ angle rotations. The typical total error budget
on these measurements is around 150 m (smaller than the baseline 200 m
chamber resolution) but smaller at the ME1 muon momentum defining ring
(75 m).

In the Endcap Muon Position Monitoring System (EMPMS) critical tracker 
plane references will be transferred to each of the Endcap system
detector layers at the CMS outer radial boundaries. Twelve interleaved
LINK Straight Line Monitors (SLMs) through the Barrel muon system are
defined by the two outer end MABs (structures holding the CCd cameras
for the barrel alignment). These MABs are connected by the Link
alignment system to the Central Tracker coordinate system as shown in
Fig.5. The Endcap Link lines transfer six (R, R) references to each
detector CSC station. There is also an Endcap Z coordinate transfer
system to all chamber layers. It consists of a concatenation of
laser-detector triangulation distance measurements between the Barrel
end MABs and carbon fiber tubes/reference surfaces on the outer boundary
of the YEn iron between all the layers of chambers. Thus diametrically
opposing (R,R,Z) link points around the endcap iron are defined. Two
possible optical beam position sensors are under development/test: ALMY,
a transparent sensor and DCOPS, an open geometry sensor using cross-hair
laser lines

![](media/image14.wmf){width="5.929861111111111in" height="3.5in"}Fig.
5: Tracker  plane transfer to the Endcap Muon System by the Link system

![](media/image15.png){width="4.478472222222222in"
height="4.509722222222222in"}

Fig. 6: Z coordinate transfer to (MEn/m) layers from references on the
MABs*.*

The Link line SLMs consist of laser+optics sources at each end of the
CMS Endcaps (ME4) projecting across CMS through a string of eight (ten
if ME4) transparent optical position sensors (ALMY or DCOPS). The two
optical sensors on the end MABs of the Barrel system define the Link
line in the tracker coordinate system. For ALMY, the bi-directional
sensors respond to both Z+ and Z- source. A bi- directional version of
DCOPS with an optical wedge has been succesfully tested. Also 20m laser
sources have been prototyped. Estimated error on Link transfer at Endcap
Link Sensors range 71- 108 μm.

Z transfer exists along all six Link SLM lines on each Endcap. The Z
tubes are rigidly connected (referenced) to the link transfer fixtures
and float (slide) in spherical bearing supports on the YEn iron. We have
tested a commercial distance sensor (OMRON Z4MW40) that works on a 40 ±
10 mm stand-off with a long term resolution (3 week measurement periods)
of 1-2 mm with a slow drift of less than 0.1 m/day. This sensor has
observed diurnal motions of 1 m. It is insensitive to light
backgrounds, fringe magnetic fields, and is thermally compensated. It
will be used to transfer a Z reference surface on the MABs without
touching them.

Between the outer boundaries of the Endcap iron discs there is a much
smaller differential motion, so we have tested another low cost
commercial distance sensor, the OMRON Z4DA01. It has a linear range of
2.5 mm at a 6 mm stand-off with a sensitivity of 2 m and long term
stability (2 weeks) of 10 m at a 20% duty cycle.

Detector resolution is insensitive to the Z coordinate and we need to
track only the large (several mm) magnetic iron motions across the local
layers. Estimated local Z errors (148 m) are dominated by transfer
block torsion errors due the endcap iron bending (129 m).

1.  **Hadron Calorimeter (HCAL)**

**Hadron Calorimeter - η coverage**

  ----------------------------------------- -----------------------------
  Barrel Calorimeter (**HB**)               ( 0 \< η \< 1.3 )

  Endcap Calorimeter (**HE**)               ( 1.3 \< η \< 3.0 )

  Forward Calorimeter (**HF**)              ( 3.0 \< η \< 5.0 )
  ----------------------------------------- -----------------------------

**Hadron Barrel Absorber**

![](media/image16.wmf){width="2.8631944444444444in"
height="2.2909722222222224in"}\
Two half barrels (HB-1 and HB+1)\
Weight: 500 Metric Tonnes\
Number of wedges: 18/half barrel\
Weight of wedge: 27.8 Metric Tonnes\
Outer Dimensions: r= 2855.0mm (flat)\
z= 4332.0mm\
Inner Dimension: r= 1690.5mm (flat)\
z= 3658.8mm

![](media/image17.png){width="3.1in" height="2.297222222222222in"}

**HB-1 and HB+1 Wedges**

Number of wedges/half barrel: 18\
Total: 36\
Extra wedges: 2 (PPP1 & PPP2 \-- Pre-Production Prototypes)\
Wedge weight: 27.8 Metric Tonnes\
Outer Dimensions: r= 2855.0mm (flat)\
z= 4332.0mm\
w= 997.3mm\
Inner Dimension: r= 1690.5mm (flat)\
z= 3658.8mm\
w= 637.1mm\
Phi Angle subtended: 20 degrees\
Number of plates: Stainless Steel: 2\
Brass: 29\
Number of bolts/wedge: 2200\
Total number of bolts: 76,000\
spares: 8,000

![](media/image18.png){width="2.75in" height="2.6256944444444446in"}\
\
**\
**

**Hadron Barrel Megatiles**\
\
Megatiles are made of scintillator inserted into slots between wedge
plates. Slots are arranged in layers - Number of layers = 17 (0:16).
Megatiles consist of set of mechanically bound, but optically separated
tiles. Charged particle ionazation induced light pulses will be
collected by wavelength shifting (WLS) fiber from each tile. WLS fibers
are\
trapped inside sigma-shaped grooves machined in scintillator. WLS fibers
fused to clear fibers arranged to terminate into optical connector.
Signals from megatile routed via optical cable to Readout Box. Innermost
layer is part of ECAL system: - Layer 0. Outermost layer attached to
outer surface of HB absorber: Layer 16 Nominal Tile size: η x ϕ = 0.087
x 0.087 (5 degrees in phi or 1/4 wedge in phi).\
\
\
**\
Layers 0 (inter)**\
\
phi segmentation : 2x5deg megatiles + 1x10deg megatile\
Central megatile: 1 per layer\
length = wedge length (3165 mm)\
width = 10 degrees in phi or 1/2 wedge size (320 mm)\
t= 13 mm\
scintillator thickness = 9.0 mm BC-448\
Edge megatiles: 2 per layer\
length = wedge length (3074 mm)\
width = 5 degrees in phi or 1/4 wedge size (154 mm)\
t= 13 mm\
scintillator thickness = 9.0 mm BC-448

**Layer 16 (outer)**\
\
phi segmentation :4x5deg megatiles/wedge\
z= 4332 mm (half barrel)\
w= 898 mm (total width)\
t= 13 mm\
scintillator thickness = 9.0 mm SCSN-81

**Tile count:**\
\
layer 0 : 4 (phi) x 15 (eta)\
layer 1- 2: 4 (phi) x 17 (eta)\
layer 3- 8: 4 (phi) x 16 (eta)\
layer 4-14: 4 (phi) x 15 (eta)\
layer 15 edge : 2 (phi) x 15 (eta)\
layer 15 central : 2 (phi) x 14 (eta)\
layer 16 : 4 (phi) x 14 (eta)\
\
\
**Total number of towers/wedge: 68**

with 2 readout channels: 56\
with 3 readout channels: 12\
Total number of readout channels/wedge: 56\*2 + 12\*3 = 148\
\
\
**Total amount of 3.7 mm scintillator/wedge: 48.7 m2\
Total amount of 9.0 mm scintillator/wedge: 5.5 m2**\
**\
Megatile material/wedge:**

Tyvek: 108.4 m\^2\
Tedlar: 108.4 m\^2\
Plastic grooved covers (1mm on bottom and 2mm on top): 108.4 m\^2\
\
Total length of WLS fiber/wedge (0.94mm dia): 590 m\
Total length of clear fiber/wedge (0.94mm dia) : 990 m\
\
Number of optical connectors on megatiles: 4 x 17 = 68\
Number of optical cables/wedge: 4 x 17 = 68\
Number of optical connectors on cables/wedge: 8 x 17 = 136\
Length of optical cable: 100mm to 1100mm

![](media/image20.png){width="3.4in" height="2.55in"}

#  {#section-1 .unnumbered}

# Hadron Barrel Readout Box {#hadron-barrel-readout-box .unnumbered}

Optical Signal mixed according to tower geometry into HPD\'s\
HPD\'s turn photons into electrons with 15% efficiency and a gain of
2000\
HPD signal amplified and digitized by CMS QIE electronics\
QIE asics mounted 6/board on RB backplane\
Calibration signals are distributed and monitored via RB\
Sourcery is monitored via signal readout channels\
HV/LV power distributed via RB\
Cotrols communication path in/out of RB\
\
Number of Readout Boxes = 196 +spares, (36HB, 60HOB, 36HE, and 64HF)\
Number of HPD\'s = 492 +15% spares, (36x5HB, 36x5HE, 48x2+12x3HOB)\
\
\
No. of RB\'s/wedge: 1\
No. of RB\'s/half-barrel: 18\
\
No. of (input) optical connectors: 72\
No. of optical bundles: 148\
\
No. of LED\'s/box: 2\
No. of Y11 blocks/box: 1\
No. of PIN\'s/box: 2\
\
No. of HPD\'s/box (19 pixels) : 4\
No. of HPD\'s/box (73 pixels) ; 1\
No. of HPD cookies/box: 4 + 1 = 5\
No. of HPD mounts/box: 4 + 1 = 5\
No. of signal channels/box: 148\
No. of independent calibration channels/box: ??\
No. of QIE cards/box: 25 ?\
No. of optical fibers out: 50\
No. of optical drivers: 50

![](media/image21.jpeg){width="3.8368055555555554in"
height="2.786111111111111in"}

**HB and HE Front End Electronics**

Each of the 36 HB readout boxes contains:\
25 six-channel boards\
1 TTC/Fieldbus board\
50 data links\
\
Each of the 36 HE readout boxes contains:\
36 three-channel boards\
1 TTC/Fieldbus board\
36 data links

**Hadron Calorimeter Calibration System**

**Moving wire radioactive source of Co60**.\
\
Each megatile layer will have a source tube for HB, HE and HO-B\
\
HB 2448 source tubes\
HE 2736 source tubes\
HO-B 72 source tubes per ring per layer\
Hence HO-B0: 144 source tubes\
HO-B+/-1, HO-B+/-2 = 288 tubes\
\
CMS closed, only 8 source tubes per wedge for HB and HE can be
accessed.\
None for HO-B can be accessed. CMS open, all source tubes can be
accessed.\
Moving wire source installed inside CMS:\
HB - 4; HE - 6; HF-2.\
Roving moving wire sources.\
HB - 3, HE - 2; HO-B -2.\
\
**Laser Calibration system.**

This includes HB, HE and HO-B.\
Number of Laser(s); 1 nitrogen of about 1 mJ.\
Possibly to be replaced by many blue laser (not yet on the market)\
Number of Dye cells: 1 UV to blue.\
Number of commutator: 1 with 16 laser pulse output SMA connectors.\
Number of neutral density filters: 1\
Laser control box: 1 under computer control.\
Number of quartz fibers from control room to CMS each 150m long: 16\
Number of primary splitter: 16\
Number of quartz fibers (10 and 25 m each) from splitter to optical
boxes\
2 for each HB, 2 for each HE, one for each HO-B: total 204, about 4km\
Number of calibration boxes attached to optical decoder boxes, one each\
Number for HB 36,\
Spares + PPP: 6\
Number for HE 36:\
Spares + PPP: 6\
Number for HO-B 60\
Spares + PPP: 6

![](media/image22.jpeg){width="3.122916666666667in"
height="2.342361111111111in"}

**Trigger/DAQ**

DAQ Card = 9U VME card + Aux card for optical receivers upto 48 links\
Trigger Card = 9U VME Card + Aux trigger transmitter with upto 48 1Gb
links\
Crates = 9U VME Crates\
DCC = 9U VME card + Aux card with upto 2 1 Gb/s optical fibers\
DDU = plug into DAQ card = PCI interface card with 1 Gb/s fiber input\
\
\
**TOTAL = HB+HOB+HE+HF:\
**\
286 DAQ cards\
118 Trigger Cards\
24 Crates\
27 DCC Cards\
27 DDU Cards\
\
Broken down into regions as follows.

**HV/LV PS**

1 LV & 1 HV PS/RBX\
Total number of HV PS\'s= 132 (+spares)\
Total number of LV PS\'s= 132 (+spares)

**Hadron Endcap**\
\
**Scintillator:**\
\
Megatiles range in size from 1.8m x 0.56m to 2.3m x 0.66m\
Thickness 3.7mm\
There are 36 megatiles per layer per end (10 degrees in phi)\
There are 20 layers per end\
Number of megatiles = 36x20 x2 = 1440\
There are 2 optical connectors per megatile ( total = 2x36x20 x2= 2880)\
There are 2880 optical cables (2 connectors/cable + optical fiber)\
**\
Calibration Source:**

Source tubes (wire source): one every 5 degrees in Phi, per megatile\
= 4 per wedge layer\
length: full Z-length of megatile\
stainless steel, diameter 1.27 mm\
antifriction paint inside 60cm of high-Z end\
Source tube couplers: one per tube, brass, at high-Z edge of megatile\
\
**Endcap RBX\'s**\
\
No of RBX\'s/wedge = 1\
No of RBX/s/endcap = 18\
Total number of RBX\'s = 36

**\
Hadron Endcap Photodetectors**\
\
No. of HPD\'s/wedge (19 pixels) : 4\
No. of HPD\'s/wedge (73 pixels) ; 1\
Total No. of 19 pixel HPD\'s: 144\
Total No. of 73 pixel HPD\'s: 36\
\
**Endcap FEE**\
\
Each of the 36 HE readout boxes contains:\
36 three-channel boards\
1 TTC/Fieldbus board\
36 data links

**Hadron Forward HF**\
\
**ABSORBER:**

Eta coverage : 3 to 5\
Delta eta x Delta phi : 0.175 x 0.175\
Total weight : 200 tonnes\
No of large modules : 176\
No of smaller modules : 24\
Large brick dimensions : 24 cm x 24 cm x 165 cm\
Small brick dimensions : 12 cm x 24 cm x 165 cm\
No of replaceble modules: 4\
Z_front : 11130 mm\
Z_back : 12780 mm\
R_in : 140 mm\
R_out (active) : 1300 mm\
No of grooved plate/mod : 48\
No of ungrooved plat/mod: 48\
Thick. of grooved plate : 3 mm\
Thick. of ungr\'d plate : 2 mm\
No of grooves/plate : 96 on each side\
Groove x-sec : 0.5+0.150 mm by 0.5+0.15 mm square\
Material : Steel (08YUGOST 9045-80)\
Lifting fixtures : 2 min vacuum.\
\
\
**\
READOUT BOXES**:

No of RBX\'s : 72\
Type of boxes : 2 (Type-A and Type-B)\
No of Type-A Box : 36\
No of Type-B Box : 36\
No of PMT in Type-A : 31\
No of PMT in Type-B : 24\
Optical coupling : Air-core light guides\
No of ROBox/10 degrees : 1\
No of cal units/box : 1\
No of laser fib in : 1\
No of LEDs/Box : 2\
No of PIN PD/Box : 2\
No of multipin HV/box : 1\
No of multipin sig/box : 1\
Temp control : +/- 1 C\
Gas flow : Nitrogen\
Material : Al\
: Quick connect/disconnect mechanism\
: Light tight

**PHOTODETECTORS:**

![](media/image23.png){width="3.0166666666666666in"
height="2.9444444444444446in"}**CALIBRATION:**\
\
**Radioactive Source:**\
Source type : Co\^60\
Activity : 10 mCi min\
Dimensions : point source on a wire\
No of Source tubes : 112 total (56 per side)\
: 45 degree line with 7 tubes per line\
No of Drivers : 2 (1/side)\
Laser:\
Laser source : Nitrogen (337 nm or similar)\
Wavelength range 337-500 nm\
Rate : 10 Hz max\
Pulse-to-pulse var : \< 5%\
No of photons at PMT : 10\^5 min\
No of input/box : 1 with SMA connector

2.  **TRIDAS**

The CMS Trigger and Data Acquisition System (TriDAS) is designed to
operate at the nominal LHC design luminosity of 10^34^ cm^-2^ s^-1^,
where an average of 20 inelastic events occur at the beam crossing
frequency of 40 MHz. This input rate of 10^9^ interactions every second
must be reduced by a factor of at least 10^7^ to 100 Hz, the maximum
rate that should be archived for off-line analysis. CMS has chosen to
reduce this rate in two steps. The first step (Level-1 Trigger, WBS
1.3.1) stores all data for approximately 3 μs, after which no more than
a 75 kHz rate of the stored events is forwarded to the second level.
During the 3 μs of the Level-1 trigger processing time, trigger
decisions must be made to discard a large fraction of the data while
retaining the small portion coming from interactions of interest. In the
second step (data acquisition and high-level Trigger, WBS 1.3.2) the
data are read out of the Front-End electronics and stored in \~ 400 deep
dual-ported memories (DPMs) for up to a second. The DPMs feed their data
via a large switching fabric to \~ 400 farms of commercial CPUs. The
latter run physics selection algorithms in order to reduce the maximum
input event rate from 75 kHz to no more than 100 Hz.

+----------------------------------+-----------------------------------+
| The architecture described above | ![](media/image24.                |
| is very similar to those of      | wmf){width="2.4694444444444446in" |
| current collider experiments.    | height="2.332638888888889in"}     |
| The one major difference is the  |                                   |
| absence of a dedicated Level-2   | Figure 1.3.1: Block diagram of    |
| trigger that provides an         | the CMS TriDAS                    |
| intermediate rate reduction of   |                                   |
| roughly another factor of 100,   |                                   |
| before events are forwarded to   |                                   |
| the processor farm. As an        |                                   |
| example, in the CDF system, the  |                                   |
| Level-2 trigger is expected to   |                                   |
| provide a reduction of events    |                                   |
| sent to the computer farm (which |                                   |
| runs the Level-3 filter). In the |                                   |
| CMS design, such a reduction is  |                                   |
| going to be provided by the      |                                   |
| processor farm which will filter |                                   |
| events in two steps, a Level-2   |                                   |
| and a Level-3 step. These two    |                                   |
| steps are referred to as the     |                                   |
| "High Level Trigger" (HLT).      |                                   |
+----------------------------------+-----------------------------------+

The main parameters of the CMS Trigger/DAQ System are listed in Fig.
1.3.2. With respect to the parameters listed in the CMS Technical
Proposal (and also assumed at the 1997 DOE review of CMS) one major
change is the decrease in the assumed maximum Level-1 trigger rate from
100 kHz to 75 kHz. This change was the result of a rescope of the TriDAS
system following a series of internal reviews by the CMS management. The
new baseline design for CMS is therefore a system capable of reading
events with an average data size of 1 MB at a rate of 75 kHz. To
maintain the future scalability of the system, each subsystem will be
designed to be capabale of handling a maximum rate of 100 kHz.

![](media/image25.wmf){width="5.7034722222222225in"
height="2.092361111111111in"}

Figure 1.3.2: Main parameters of the CMS TriDAS

**1.3.1 Trigger**

The endcap muon trigger system finds high-momentum muons consistent with
coming from the primary interaction region, allowing identification of
Higgs particles, W and Z bosons, etc. In addition, under low luminosity
conditions, the muon trigger can identify muons down to the cutoff
momentum imposed by range-out in the steel of the magnet flux return,
allowing interesting studies of rare B-particle decays.

The calorimeter trigger system provides triggers based upon the energy
profiles left in the CMS calorimeter by electrons, photons, jets and
non-interacting particles in the interesting events. It also provides
additional information for the muon trigger system for isolation and
minimum ionization signal identification.

**1.3.1.1 Endcap CSC Muon Trigger**

The baseline CMS muon system currently consists of 4 stations of
chambers in the barrel region and 3 stations in the endcap region. In
the barrel detector, these are drift chambers, whereas in the endcap
detector, they are Cathode Strip Chambers (CSC's). The layout of these
systems is shown in profile in Figure 1. Each station of CSC contains
overlapping 10 or 20-degree wide chambers, and each chamber contains 6
measurement layers. In each measurement layer, anode wires are read out
to measure the non-bend (imprecise) coordinate and radial cathode strips
are read out to measure the bend (precision) coordinate. A muon produces
a "stub" in each dimension. All of the on-chamber electronics for muon
identification, including trigger, is considered and is budgeted as part
of the Endcap Muon system. The off-chamber trigger electronics which
collects muon stubs from the chambers, sends the stub information
"upstairs" on optical fibers, and links the muon stubs into a muon track
of known momentum and direction is known as the Muon Regional Trigger
System (WBS item 3.1.1) portion of the US-CMS Trigger/Data Acquisition
(TRIDAS) system, WBS item 3.

The on-chamber Cathode and Anode cards, which find projections of muon
stubs in strip and wire views, respectively, are mounted on the surfaces
of the CSC chambers. In the 3-station endcap muon system, there are 2016
cathode strip cards and 1800 anode wire cards, mounted on 432 CSC
chambers. There is one on-chamber card per CSC chamber, called the
Motherboard, which does the time correlation of the two views and sends
the stub information on via copper to a Muon Port Card (MPC). The
on-chamber circuitry up to the cables going from Motherboards to Muon
Port Cards is considered as part of the Endcap Muon system - from there
on, the circuitry is part of the TRIDAS system. The Muon Port Cards
assemble muon trigger data from a 60-degree φ swath and pass it on via
Gbaud optical links to the Track Finder crates. The Track Finder crates
link together the muon stubs into tracks and determine the muon momentum
vectors for use in the CMS Global Muon trigger. The drift tube muon
trigger, the global muon logic, and the global Level 1 trigger
electronics are responsibilities of European groups. A block diagram
showing the overall structure of the CSC muon trigger electronics is
shown in Fig. 1.3.3.

The major portions of the off-chamber muon trigger electronics contained
in WBS 3.1.1 are therefore Muon Port Cards (MPC), optical data and clock
links, and track finder crates containing Sector Receiver (SR) cards,
Sector Processor (SP) cards, Clock and Control Cards (CCC), and
ancillary logic and cabling.

![](media/image26.png){width="3.1694444444444443in"
height="4.204861111111111in"}

A Muon Port Card (MPC) receives data from nine Motherboards within a CSC
station. In the first station, this is a φ interval of 30 degrees, while
in the other stations this is a φ interval of 60 degrees. The Muon Port
Card sends the data "upstairs" via fast optical links to a CSC Track
Finder crate. The MPC\'s are located near the outer periphery of the CSC
chambers to keep copper cabling distances acceptably short. There are 12
Muon Port Cards in CSC station ME1 in each endcap, and 6 Muon Port Cards
in each of the later stations, for a total of 48 MPC. It takes 7 Gbaud
optical links per MPC to send the information from up to 3 muon stubs to
the Track Finder. The front-end electronics is designed to present a
priority-ordered set of muon stubs to the Muon Port Cards, where the
priority is determined by number of layers hit, a rough measure of
momentum (local bending), and consistency with arrival from the primary
vertex. Within the MPC, priority-encoding circuitry is included to
select the best muon stubs in the case that more than three stubs arrive
simultaneously. The MPC also handle the function of receiving master
clock signals via TTC interface and fanning them out to the front-end
CSC chamber electronics.

The layout of the muon Track Finder contains separate racks for barrel
(DT), endcap-only (CSC), and overlap processor regions. Within the
barrel system, the Track Finders are organized by wheel. Each VME crate
handles 180 degrees in phi of track finding. Signals from the CSC system
come to the Track Finder on optical links, and are received in the
CSC-only section. A conception of the system, shown below, contains 9
racks, each of which contains 2 VME crates. The CSC-only and overlap
Track Finders (U.S. responsibilities) are contained in 4 racks/8 crates.

Data comes from the Muon Port Cards (MPC) on optical fibers to the
CSC-only Track Finder crates. Each MPC sends data representing 60
degrees in phi of one muon station (with the exception of station 1,
which sends data in 30-degree sub-sectors. The card that receives these
signals is called the Sector Receiver (SR).

The Sector Receiver card does 2D to 3D muon stub conversion, alignment
corrections, and data reformatting. It then sends muon stub data to the
Sector Processor (SP) module on the crate backplane. If the Sector
Receiver is being used in the CSC-only crate, it must also replicate the
data and send it on to the Overlap crate on copper. If the Sector
Receiver is being used in the Overlap crate, it must receive its input
data over copper. After the data is received by the Sector Receiver
cards, it can be reformatted by look-up tables into whatever format is
convenient for the Sector Processor track finding.

There are three Sector Processors per crate, each handling 60 degrees in
phi. In the baseline design, up to three muon stubs are transmitted from
each MPC on six optical fibers. The Sector Receivers are designed to
receive 15 optical fibers carrying 270 data bits. Depending on whether
we have three or four endcap muon stations, two or three MPC\'s are
connected to each Sector Receiver. The Sector Receiver, which is
connected to the two ME1 MPC\'s in the 60 degree sector, combines the
information before transmission to the Sector Processor. Two Sector
Receivers send data to each Sector Processor.

**1.3.1.2 Regional Calorimeter Trigger**

The calorimeter level 1 trigger system baseline design receives digital
trigger sums via copper links from the front-end electronics system in
the electronics counting house. The data includes energy on an eight bit
compressed non-linear scale and a fine grain ID bit determined from the
data used to make the energy sums. The data for two HCAL or ECAL trigger
towers for the same crossing will be sent on a single copper serial link
in eighteen total bits accompanied by five bits of error detection. One
additional bit is used to set the link into either control or data
modes.

The calorimeter regional crate system (WBS 3.1.2) portion of the US-CMS
Trigger/Data Acquisition (TRIDAS) system, WBS item 3 consists of 19
calorimeter processor crates covering the full calorimeter. Eighteen
crates are dedicated to the barrel and two endcaps. These crates are
filled out to an η of 2.6, with partial utilization between 2.6 and 3.0.
The remaining crate covers both Very Forward Calorimeters.

Each calorimeter regional crate transmits to the calorimeter global
trigger processor its sum E~t~, E~x~ and E~y~. It also sends its 4
highest-ranked electrons and 4 highest energy jets along with
information about their location. The global calorimeter trigger then
sums the energies and sorts the electrons and jets and forwards the top
four calorimeter-wide electrons and jets, as well as the total
calorimeter missing and sum E~t~ to the CMS global trigger.

The regional calorimeter trigger crate, shown schematically in Fig.
1.3.4, has a height of 9U and a depth approximately of 700mm. The front
section of the crate is designed to accommodate 280mm deep cards,
leaving the major portion of the volume for 400 mm deep rear mounted
cards.

![](media/image27.wmf){width="4.779861111111111in"
height="2.9944444444444445in"}

Figure 1.3.4. Schematic view of a typical Calorimeter Level 1 Regional
crate.

The majority of cards in the Calorimeter Level 1 Regional Processor
Crates, encompassing three custom board designs, are dedicated to
receiving and processing data from the calorimeter. There are eight rear
mounted Receiver cards, eight front mounted Electron Isolation cards,
and one front mounted Jet Summary card for a total of 17 cards per
crate. The high density high-speed 160 MHz data flow is achieved by
plugging all cards into a custom "backplane" with about 1400
point-to-point differential links in addition to full VME bus.

The Receiver card is the largest board in the crate. It is 9U by 400mm.
The rear side of the card receives the calorimeter data from optical
fibers, translates from fiber to copper, and converts from serial to
parallel format. The front side of the card contains circuitry to
synchronize the incoming data with the local clock, and check for data
transmission errors. There are also lookup tables and adder blocks on
the front. The lookup tables translate the incoming information to
transverse energy on several scales. The energy summation tree begins on
these cards in order to reduce the amount of data forwarded on the
backplane to the Jet Summary card. Separate cable connectors and
buffering are also provided for inter-crate sharing.

The transverse energy for each of the two 4 x 4 trigger tower regions is
independently summed and forwarded to the Jet Summary card. On the Jet
Summary card these E~t~ sums are used to continue the energy summation
tree and also compared against a threshold to determine whether any
sub-region contained jets. The Et sums are applied to a set of lookup
tables to generate E~x~ and E~y~ for each 4 x 4 region. A separate adder
tree is used to sum up E~x~ and E~y~ from the regional values.

In the present baseline design, the Receiver card also has separate
lookup tables to provide linearized 7-bit ECAL transverse energy and H
versus E comparison bits, for the electron/photon algorithm. These data
are staged to both the cards within the crate at 160 MHz on the
backplane, and to the neighboring crates on cables at 40 MHz. The
Electron Isolation card receives the data staged to it from the Receiver
cards and implements the algorithm discussed above in custom ASIC's. The
E~t~ and isolation bits of the highest E~t~ electron/photon candidate
from each of the two 4 × 4 trigger tower regions handled by the Electron
Isolation cards are passed to the Jet/Summary card. The Jet/Summary card
separately sorts these data from all eight Electron Isolation cards in
the crate to obtain top four "non-isolated" and "isolated"
electron/photon candidates, and passes them on to the global trigger on
cables at 40 MHz.

######## **Trigger Parameters Tables** {#trigger-parameters-tables .unnumbered}

Table 1 shows the input data to the US CMS part of the Level 1 trigger
processors, the CSC Track Finder and the Calorimeter Regional Trigger,
Table 2 shows the output of these systems to the Global Muon and Global
Calorimeter Level 1 Trigger Processors.

+-------------------------+---------------------------+----------------+
| System                  | Input Level 1             | Input Level 1  |
|                         | Segmentation per half     | Data           |
+-------------------------+---------------------------+----------------+
| Muon Drift Tubes        | 2457 φ x 80 η x 4 R       | 8 bend bits    |
+-------------------------+---------------------------+----------------+
| Muon CSC                | 2457 φ x 2048 η x 3 Z     | 6 bend bits    |
+-------------------------+---------------------------+----------------+
| ECAL (0 \< \|η\| \<     | 72 φ x 17 η               | 8 bits energy  |
| 1.479)                  |                           |                |
|                         |                           | 1 bit fine     |
|                         |                           | grain          |
+-------------------------+---------------------------+----------------+
| HCAL (0 \< \|η\| \<     | 72 φ x 17 η               | 8 bits energy  |
| 1.479)                  |                           |                |
|                         |                           | 1 bit depth    |
|                         |                           | profile        |
+-------------------------+---------------------------+----------------+
| ECAL (1.479 \< \|η\| \< | 72 φ x 4 η                | 8 bits energy  |
| 2.16)                   |                           |                |
|                         |                           | 1 bit fine     |
|                         |                           | grain          |
+-------------------------+---------------------------+----------------+
| HCAL (1.479 \< \|η\| \< | 72 φ x 4 η                | 8 bits energy  |
| 2.16)                   |                           |                |
|                         |                           | 1 bit depth    |
|                         |                           | profile        |
+-------------------------+---------------------------+----------------+
| ECAL (2.16 \< \|η\| \<  | 72 φ x 2 η                | 8 bits energy  |
| 2.60)                   |                           |                |
|                         |                           | 1 bit fine     |
|                         |                           | grain          |
+-------------------------+---------------------------+----------------+
| HCAL (2.16 \< \|η\| \<  | 36 φ x 2 η (φ data        | 8 bits energy  |
| 2.60)                   | doubled)                  |                |
|                         |                           | 1 bit depth    |
|                         |                           | profile        |
+-------------------------+---------------------------+----------------+
| ECAL (2.60 \< \|η\| \<  | 72 φ x 1 η                | 8 bits energy  |
| 3.0)                    |                           |                |
+-------------------------+---------------------------+----------------+
| HCAL (2.60 \< \|η\| \<  | 36 φ x 1 η (φ data        | 8 bits energy  |
| 3.0)                    | doubled)                  |                |
|                         |                           | 1 bit depth    |
|                         |                           | profile        |
+-------------------------+---------------------------+----------------+
| VFCAL (3.0 \< \|η\| \<  | 12 φ x 12 η               | 8 bits energy  |
| 5.0)                    |                           |                |
|                         |                           | 1 bit jet tag  |
+-------------------------+---------------------------+----------------+

Table 1. Input Data to the US CMS Level 1 Trigger Processors[^4].

+-------------------+----------------------------+--------------------+
| System            | Output Level 1             | Output Level 1     |
|                   | Segmentation per half      | Data               |
+-------------------+----------------------------+--------------------+
| Muon Drift Tubes  | 256 φ x 32 η               | 5 p~T~ bits        |
|                   |                            | (nonlinear)        |
+-------------------+----------------------------+--------------------+
| Muon CSC          | 256 φ x 32 η               | 5 p~T~ bits        |
|                   |                            | (nonlinear)        |
+-------------------+----------------------------+--------------------+
| ECAL & HCAL       | 18 φ x 6 η                 | 4 highest E~T~     |
|                   |                            | electrons, jets    |
|                   |                            |                    |
|                   |                            | 10 bits energy     |
+-------------------+----------------------------+--------------------+
| ECAL & HCAL       | 9 φ                        | E~T~, E~x~, E~y~   |
|                   |                            | in 10 bits         |
+-------------------+----------------------------+--------------------+
| VFCAL (3.0 \<     | One Region for both halves | E~T~, E~x~, E~y~   |
| \|η\| \< 5.0)     |                            | in 10 bits, jet    |
|                   |                            | tag                |
+-------------------+----------------------------+--------------------+

Table 2. Output Data from the US CMS Level 1 Trigger Processors.

2.  **Data Acquisition**

The architecture of the CMS DAQ System is shown in Fig. 1.3.2.1. Upon
the reception of a Level-1 accept signal, the front-end electronics are
read out by a set of \~ 400 modules (Readout Units, RU) which buffer the
event during the Event Building process. The RUs are connected to a
number of Filter Units (FUs) which contain processors that analyze the
events received from the RUs. The RUs are connected to the FUs via a
high-bandwidth switch. A central intelligence, the Event Flow Control
(EFC) system, synchronizes the RUs and FUs by allocating each event
accepted by the Level-1 Trigger to the next available Filter Unit.
Another subsystem, "Controls" is responsible for all configuration
setting, monitoring and user interface.

![](media/image28.wmf){width="4.170833333333333in"
height="2.0208333333333335in"}

Figure 1.3.2.1: Schematic of the architecture of the CMS TriDAS.

As explained in the overview of the TriDAS (section 1.3) the processor
farm executes both the "Level-2" and the "Level-3" triggering steps. The
Level-2 step is executed based on only a reduced amount of data from the
event in question. If the event is rejected in this step, then the EFC
is told to delete the rest of the data belonging to the event from the
remaining RUs. This process is shown schematically in Fig. 1.3.2.2.

![](media/image29.wmf){width="4.760416666666667in"
height="3.5236111111111112in"}

Figure 1.3.2.2: Schematic of the principle of the CMS High Level Trigger
system.

The overall effect of this two-step process is to reduce the total
required switch bandwidth. As an example, assuming a Level-2 rejection
factor of 10, and an average fraction of data required by the Level-2
step of 25% of the total event size, the switch bandwidth required to
send events to the Filter Units (assuming 100 kHz of Level-1 events) is
reduced from 600 Gb/s to 200 Gb/s.

As an example, given an event that has been accepted by the Level-1
trigger system based on the inclusive electron criteria, the Filter Unit
allocated by the EFC to process this event will be provided with the
calorimeter data corresponding to this event. Data from the tracking
detectors (whose data size is roughly three times larger than the data
size from the calorimetry) will not be sent to the FU in question. The
Filter Unit, in turn, will pass the event to one of the processors
(Filter Nodes, FN) attached to it. The FN allocated to process the
event, proceeds to analyze the information received by running an
algorithm which first confirms the Level-1 trigger decision. The data
provided to the processor correspond to the full detector granularity
and resolution. Therefore, even a simple re-application of the Level-1
trigger algorithm can result in sharper thresholds at Level-2. More
elaborate algorithms based only on calorimeter data are also foreseen.
The Level-2 filter is expected to provide at least a factor 10 in rate
reduction.

If an event does not pass the Level-2 filter, then the FU processing it
will instruct the Event Flow Control System to erase the rest of the
data corresponding to this event from the remaining RUs. If the event
passes the Level-2 filter, then the FU processing it will request the
rest of the data belonging to the event in question from the Event Flow
Control.

######### US Responsibility {#us-responsibility .unnumbered}

The US is responsible for providing the Event Manager part of the Event
Flow Control and the SFI part of the Filter Units (i.e. the entire FUs
but excluding the Filter Nodes, i.e. the processors). The total number
of modules to be delivered are: one Event Manager (EVM) and 432 SFIs
(including spares).

######## **Filter Units** {#filter-units .unnumbered}

The requirements for the Filter Units are shown in Fig. 1.3.2.3. There
are two high-speed (event-data) ports and two (slower) control and
monitor ports. The Input data port must be capable of reading data from
the switch ports. The Output data port must be capable of feeding a
number of CPUs (Filter Nodes) that run the HLT algorithms. With an event
size of 1MB and 400 FUs, each FU will contain roughly 1 MB of event data
at a rate of 150 Hz. However, the FUs are designed to function at rates
of up to 100 kHz, which translates to 200 Hz. The maximum sustained
average data per FU is thus 200 MB/s

![](media/image30.wmf){width="4.611111111111111in"
height="3.709722222222222in"}

Figure 1.3.2.3: I/O Requirements for the Filter Unit (FU)

####### **FU: Functional Decomposition**

The functions of the Filter Unit are summarized in Fig 1.3.2.4. The
Filter Unit is split into two logical parts: the SFI and the CPUs. The
SFI is functionally split into three stages:

-   Input, performed by the Filter Unit Input (FUI),

-   Event Storage, performed by the Filter Unit Memory (FUM) and

-   Event Output, performed by the Filter Unit Output (FUO).

The Control and Monitoring tasks are performed by the Filter Unit
Supervisor (FUS) intelligence.

![](media/image31.wmf){width="5.697916666666667in"
height="4.375694444444444in"}

Figure 1.3.2.4: Functional Decomposition of the Filter Unit

The interconnections required for data traffic by the FU are:

> 1\. FUI bus: a good candidate is the PCI bus (66 MHz, 64 bits)
>
> 2\. FUO bus: same as the FUI bus
>
> 3\. CPU bus: this could be either a workstation bus (connecting the
> SFI to multiple CPUs) or a network connection (e.g. Ethernet in
> sub-farm architecture)

The interconnections required for the control traffic of the FU are:

> 1\. Level-2/3 request data message. This message will be sent to the
> Event Manager, via the Filter Control Network (FCN) and indicate to
> the EVM which Readout Units should send their data for the next step
> in the Event Building process. There are no strict latency
> requirements on this message. A good candidate is a commercial network
> like Ethernet.
>
> 2\. Control and Status Network. This is a standard commercial network.

#######   {#section-2 .unnumbered}

####### **FU: Current Prototypes** {#fu-current-prototypes .unnumbered}

In the current R&D program, the FU functionality and performance is
being investigated using two complementary approaches:

> 1\. A CMS-designed module (VORTEX) which provides, via the Texas
> Instruments C80 microprocessor, the full functionality of the FUI, FUM
> and FUO.
>
> 2\. A sandwich of modules, consisting of a special-purpose FPGA memory
> module for the FUM, and two I/O modules: currently based on the Intel
> I/O Processor (IOP) family --- i960RP.. In this option, the FUI, FUO
> and FUM modules are identical to the equivalent modules in the CMS
> Readout Units.

Both approaches use the PCI bus for the mechanical mounting and electric
power supply. The PCI bus is used for both the FUI and FUO buses. The
FUS functionality is implemented via an external CPU. In solution 2, the
workstation CPU is used to implement the FUS.

######### Event Flow Control {#event-flow-control .unnumbered}

The requirements for the Event Flow Control subsystem are shown in Fig.
1.3.2.5. The EFC should be capable of sending commands to up to 500 RUs,
at a rate of up to 100 kHz, receiving commands (at the same maximum
rate) from up to 500 FUs, and also assign FUs to each event that passes
the Level-1 trigger (at a rate of up to 100 kHz). Again, in the CMS
baseline, the nominal rate is 75 kHz, but the EFC is also designed to
operate at up to 100 kHz. The networks implementing this communication
are relatively low-bandwidth but also low-latency networks.

![](media/image32.wmf){width="4.967361111111111in"
height="3.7777777777777777in"}

Figure 1.3.2.5: I/O Requirements for the Event Flow Control subsystem

**EFC: Functional Decomposition**

The functions of Event Flow Control (EFC) are summarized in Fig 1.3.2.6.
The EFC is split into three logical parts: the Event Manager and the two
communication networks, the Readout Control Network (RCN) and the Filter
Control Network (FCN).

![](media/image33.wmf){width="5.6875in" height="5.026388888888889in"}

Figure 1.3.2.6: Functional Decomposition of the Event Flow Control
subsystem

The interconnections required for the EFC control traffic are:

> 1\. Readout Control Network. This consists of two sub-networks, the
> RUI Control and the RUO Control. They (may) be different due to the
> different latency requirements on the RUI and RUO.
>
> 2\. Filter Control Network. This consists of two sub-networks, the FUI
> Control and the FUO control. This second network is optional.

In the current R&D program, the EFC functionality and performance is
being investigated using an Event Manager which is a software process
running on a CPU, coupled with either a VME interface or a fast Ethernet
interface.

1.  **Electromagnetic Calorimeter (ECAL)**

**Technical Description.**

The deliverables for the electromagnetic calorimeter fall into three
categories three categories: Avalanche Photodiodes, Front-end
electronics and the Calibration Monitor Light Source.

**1.4.1. Avalanche Photodiodes. (36,000)**

Avalanche photodiodes (APD) are semiconductor diodes with internal
electronic gain. There are two APD's per crystal in the barrel
electromagnetic detector each with an active area of 25 mm^2^. The APD
operating gain will be 50, the ambient temperature of 18^o^C. The
anticipated neutron flux for 10 years is 2 x 10^13^ neutrons/cm^2^. The
APD parameters are given in Table 1.4.1

# Table 1.4.1 {#table-1.4.1 .unnumbered}

+----------------------------------------------+-----------------------+
| Active Area                                  | 5 x 5 mm^2^           |
+----------------------------------------------+-----------------------+
| Operating Voltage                            | \< 500 V              |
+----------------------------------------------+-----------------------+
| Capacitance                                  | \<120 pF              |
+----------------------------------------------+-----------------------+
| Serial resistance                            | \< 5                 |
+----------------------------------------------+-----------------------+
| Dark Current at M = 50                       | \<10 nA               |
+----------------------------------------------+-----------------------+
| 1/M \* dM/dV (voltage sensitivity)           | \< 5%/^o^C            |
+----------------------------------------------+-----------------------+
| 1/M \* dM/dT (temperature sensitivity)       | \< 2.5%/^o^C          |
+----------------------------------------------+-----------------------+
| Spread of operating voltage                  | \< 5V                 |
+----------------------------------------------+-----------------------+
| # Excess Nois                                | \< 2.3 at M = 50.     |
| e Factor  {#excess-noise-factor .unnumbered} |                       |
+----------------------------------------------+-----------------------+
| Passivation Layer                            | Si~3~N~4~             |
+----------------------------------------------+-----------------------+
| Quantum Efficiency at 420 nm                 | \> 70%                |
+----------------------------------------------+-----------------------+
| Dark Current after 2x10^13^ neutrons/cm^2^   | \< 5 A               |
+----------------------------------------------+-----------------------+
| Survival rate                                | 99.8%                 |
+----------------------------------------------+-----------------------+

The total number of components required for the ECAL are 120,400, with
2,000 spares. The US is responsible for the delivery of 36,000 of
these.The design and development of the APD was shared with PSI. The
final engineering run is a US responsibility as is a pre-production run
of 2000 APD's.

Responsibility for QA/QC for the APD's is shared with PSI.

**1.4.2 Electronics.**

The principle items for which the US are responsible are:

1)  The design, test, production and verification of a custom radiation
    hard integrated circuit to be used in the front-end readout signal
    acquisition and digitization. (FPU)

2)  The design, test, production and verification of a custom radiation
    hard integrated circuit to be used in the conversion of the output
    signal from the ADC to a serial data stream for fiber-optic data
    transmission.(Bit Serializer)

3)  The design, production and verification of the front-end readout
    card, which houses the front-end readout circuitry.

Additional items contained within this element include R&D on
radiation-hard power regulation systems, needed to provide power for the
front-end readout electronics, and on the specification and radiation
hardness assurance of a commercial analog-to-digital converter circuit
which will be used in the front-end readout to digitize the signals.

![](media/image38.wmf){width="0.41023622047244096in"
height="0.5964566929133859in"}

Figure 1.4.1 Schematic of the Very Front End Electronics Readout.

**The FPU readout chip for the barrel front-end readout.**

Deliverables: 61,200 pieces.

Functionality: The output of the two preamplifier outputs will be spilt
between four amplifier channels 1, 8 and 32. The highest output which is
not in saturation is selected by internal logic and routed to the
output. Operationally the device works like a multi-ranging
sample-and-hold operating at 40 mHz. The operation is shown schmatically
in Figure 1.4.2.

![](media/image39.wmf){width="1.0043307086614173in"
height="1.197244094488189in"}![](media/image40.wmf){width="1.0043307086614173in"
height="1.197244094488189in"}![](media/image41.wmf){width="1.0043307086614173in"
height="1.197244094488189in"}![](media/image42.wmf){width="1.0043307086614173in"
height="1.197244094488189in"}![](media/image43.wmf){width="1.002755905511811in"
height="1.1952755905511812in"}![](media/image44.wmf){width="1.002755905511811in"
height="1.1952755905511812in"}![](media/image45.wmf){width="1.0161417322834645in"
height="1.2110236220472441in"}

Figure 1.4.3 Schematic representation of the Bit Serializer.

**1.4.3 Monitor Light Source**

The light source will be a ND:YLF laser from Photonics. Model GM-30. The
light from this high-power laser will be shifted to the suitable
frequency for the lead tungstate crystals (420 nm) and distributed using
a computer controlled optical splitter.

The light monitoring system is designed to inject light pulses into each
individual PWO crystal to measure the optical transmission of crystals.
The pulses are distributed via an optical fiber system organized into
three levels: a light source and high level distribution system (LSDS)
which sends pulses to a selected calorimeter element (1/2 barrel
supermodule or group of endcap supercrystals), and a two lower level
distribution system mounted on each calorimeter element which delivers
the pulses to PWO crystals. The relative calibration of the injected
light for each group of crystals is achieved by simultaneous injection
on reference PN silicon photodiodes included in the distribution system.
Calorimeter elements are pulsed serially to limit the power requirement
to the light source, the size of data transfers, as well as low voltage
current demands. The system is designed to continuously monitor the
calorimeter in one of two operational modes:

1\. Continuous In-fill monitoring during 3 us gaps in every 88.924 us in
the LHC beam structure.

2\. Stand-alone monitoring runs outside LHC fills to follow the recovery
of the PWO crystals.

The principal goal of the system is the monitoring of any short-term
evolution of the crystals\' light transmission for intercalibration. The
system will also be used to checkout the entire crystal-readout chain
during assembly, and will permit a rapid survey of the full CMS ECAL
during installation or after long shutdowns. Furthermore, the light
monitoring system can be used to measure response linearity of the PWO
crystal\'s photodetector and its readout chain from an equivalent energy
of 500 MeV up to 100 GeV, representing 5 X 10^4^ to 10^7^ photons
injected at the crystal, respectively. This should complement
measurements with electronic charge injection at the preamplifier level
which do not test the photodetector, but would have a larger dynamic
range.

The construction responsibility of the entire monitoring system is
shared by Caltech and Saclay groups. While Caltech is responsible for
the construction of the light source and high level distribution system
(LSDS), Saclay group is responsible for the lower level distribution
chain and the reference PN diode readout.

The LSDS provides light pulses at two wavelengths, one at the emission
peak of the doped PWO crystal (\~420 nm) and the other at peak of pure
PWO crystal (\~510 nm). (Note, this is our present knowledge. We have to
test new Nb/Y doped samples from BTCP and Sb doped samples from SIC to
reach conclusion.) The pulse length is 20-40 ns of full width to match
the electronics readout. It also provides up to 10\^7 photons per pulse
per crystal, which corresponds to 100 GeV equivalent in dynamic range.
Since the overall optical transmission efficiency from the light source
to individual crystal is better than 5 x 10^-8^, the maximum pulse
intensity sent to level-2 fanout is required to be 0.2 mJ/pulse. The
light source is also triggerable at a rate of 1 to 11 kHz, synchronized
to the 3 s beam gap in LHC beam structure. The exact operation rate
will depend upon the fraction of the 3 us gaps really used for
monitoring. The LSDS switches the light pulses to one designated ECAL
barrel supermodule half or endcap Dee half. This reduces the total power
requirement to the light source. The LSDS has also an ability to send
the light pulses of defined intensity to each individual crystal by
monitoring the pulse intensity sent to level-2 fanouts and adjusting the
light source intensity correspondingly.

The LSDS consists of four components: a laser system, a mechanical
fiberoptical switch, a pulse intensity monitor and a PC-based control
system. We plan to use a laser based light source consisting of two
Q-switched GM-30 Nd:YLF lasers and one TU-UV tunable titanium doped
sapphire laser. The GM-30 green laser is a commercial available pump
laser, designed for scientific applications. It is based on intracavity
frequency doubling technology via LBO nonlinear crystal. Intracavity
high peak power of fundamental beam makes efficient frequency conversion
to 527 nm green laser beam. Folded resonator combines both green laser
beams generated in two directions into one single laser output. The
Nd:YLF crystal medium is continuously pumped by a Krypton arc lamp. With
the Q-switch on, the Q of the cavity is kept low to prevent lasing
action. When the Q-switch is off, the Q of the cavity is immediately
changed to a high level, and stored energy is released in a short time
to produce short, intensive laser pulse. In our system, one GM-30 is
used as a pump for the TU-UV and the other GM-30 is used for a linear
amplifier to achieve the designed intensity. The TU-UV Ti:Sapphire is a
pumped, intra-cavity, frequency doubled laser, and is also commercially
available. The use of TU-UV Ti:Sapphire laser enables tunable
wavelength.

This laser system will provide light pulses of up to 0.4 mJ/pulse with a
pulse width of 20-40 ns and a repetition rate of up to 11 kHz. The pulse
to pulse intensity stability is about 3%. The laser system may be
triggered by an external TTL signal with a delay about 4 us. The trigger
delay jitter is less than 10ns, and can be improved to about 3 ns if
required. The output of the laser system is optically coupled to the
fiberoptical switch, and the operation of the laser system is controlled
by the PC in the control system through a commercial interface from
National Instruments.

The mechanical fiberoptical switch distributes light pulses from the
laser system to 80 level-2 fanouts, where 72 are barrel supermodule
halves and 8 are endcap Dee halves. The principle component of the
fiberoptical switch is a precision step motor which moves the input
fiber to couple to one of multi output fibers with an air gap. The
insertion loss of this fiberoptical switch when using 365 um fibers is
about 2 dB, and the isolation between any two channels is less than -80
dB. The average switch time between any two level-2 fanouts is about 1
s. The output fibers of the fiberoptical switch are optically coupled to
the 150 m long phi 265 um quarts fibers connected to the level-2
fanouts. The switch is also controlled by the PC in the control system
through a GPIB interface.

The light source monitor consists of 80 PIN photodiodes, which monitor
the intensity of light pulse in level-2 fanouts, and four Biplanar PMTs,
which monitor the sum of the light pulse intensities in two half barrels
and two endcaps.

The entire operation of the LSDS is controlled by the PC-based control
system, which controls and displays the working conditions of the laser
system and the fiberoptic switch. It also controls the designation and
the intensity of the light pulse sent to level-2 fanouts.

1.  **Forward Pixels (FPIX)**

Component. (required units): Pixels. (12 x 10^6^) / Sensors. (672)

The majority of the pixels (95.64%) are squares of 150 μm sides, as
indicated in Table 1. The rest of the pixels have rectangular shape and
are located on the sensors in the region between two neighboring Readout
Chips. Figure 1 indicates how the pixels are layout on the sensors
including the region between two Readout chips. Also shown are the
locations of the bumps. Figure 2 gives the dimensions of the channel
stops. Table 2 gives the dimensions of the sensors, as well as the
numbers of readout chips required for each sensor. The sensors are 250
μm thick.

The US CMS will design and procure the sensors.

Readout Chip (ROC). (4,320)

The Readout Chip is 1.0150 cm in *r*, and 0.8010 cm in *rϕ*. It is 180
μm thick. The sensors of one blade are readout with 45 ROCs. The analog
logic of the chip needs ± 2.5 V and the digital logic ± 5 V. Each pixel
dissipates 60 μW pixel. The electronics associated with each disk
consumes 250 W. The ROC communicates to the rest of the world through 20
wire-bonds.

The US CMS will procure the ROCs developed by PSI.

Blades. (96)

Each of the 4 disks is made of 24 blades configured in a 'turbine blade'
geometry. The dimensions of the blades and the position of the sensors
on the blade are given in figure 3. Also shown are the location of the
readout chips on each sensor.

The US CMS will design and build the blades including its cooling.

Disks, ½ units. (8)

There are 2 disks located on each side of the interaction region (IR).
The disks are split in 2 halves for installation reasons. These two sets
of disks are not identical but have the blades rotated such to have
point symmetry relative to the IR. Table 3 gives the position of the
disks along the z-axis, as well as the number of components on each
disk.

The US CMS will design and build the mechanical support of the disks
including the cooling.

Space Cylinders, ½ units. (8)

Two 1/2 disks are mounted on ½ unit of space cylinder. Here too, these
cylinders are split in two laves along their axis for installation
reasons.

The US CMS will design and build 8 units of ½ space cylinders.

Service Cylinders, ½ units. (8)

From z = 3 m to z = 0.5 m all the lines serving the forward pixels will
be carried by units of ½ service cylinders. These lines include power,
cooling, optical fibres for the data transmission and monitoring, and
bias voltage.

The US CMS will design and build 8 units of ½ service cylinders.

Installation.

The US CMS will supply the hardware needed to install and align the
Forward pixels in their final position.

Components along the signal path after the readout chip.(required units)

High Density Interconnect (HDI). (672)

The signals from the readout chip are collected by a multi layered
Kapton printed circuit and then carried to an interface (Port Card)
through a flex cable. There are 7 HDIs on one blade, one for each of the
7 sensors.

The US CMS will design and procure the HDIs.

Port Card. (192)

Each blade has 2 Port Cards. A Port Card is a low mass printed circuit
board with 4 ASICs and 4 laser drivers to transmit the data from the
pixels. Bias voltage to the sensors will also be distributed on the Port
Card. One of the ASIC, the Token Bit Manager (TBM), is detector
dependent and will be designed by the US CMS group. The other 3 ASICs,
the CCU (Communications Control Unit), the CDU (Detector Control Unit),
and the PLL (Phase Locked Loop), are common to the CMS trackers.

The US will design and build the Port Cards and the TBM. It will
purchase the three ASICs: CCU, CDU and PLL.

Optical Links. (768)

Each Port Card sends the data to ADCs through 100 m long optical fibres.
This system including laser drivers, optical fibres and receivers are
common to all the CMS trackers. The encapsulation of the optical driver
must be redesigned because is too massive for the pixels given their
proximity to the IR and the concern to keep the material budget to a
minimum. The data rates of the Forward pixels is given in Table 4.

The US will redesign the encapsulation of the optical link and procure
the optical links as well as purchase the other components of this
system.

Front End Controller (FEC). (768 ch.)

Are located in the counting room, receive the signals from the optical
fibers and deliver them to the ADCs. They are common to the CMS tracking
system and built in 64 channel modules.

The US CMS will procure 14 FECs modules, each one with 64 channels.

ADCs. (768 ch.)

Eight bits VME ADCs will decode the signals. These ADCs are produced in
modules of 64 channels. The group from Vienna, members of the Barrel
effort, will design these ADCs.

The US CMS will procure 14 ADCs each one with 64 channels.

Services.

The US CMS will procure the necessary power supplies, the cables, and
the chiller for cooling the electronics on the blades and the Port
Cards.

+-----------------+-------+-------+-------+-------+--------+--------+
| **Pixel size    | # Ch  |       |       |       |        | **     |
| \[μm\]**        | ips / |       |       |       |        | Pixels |
|                 |  Sens |       |       |       |        | /**    |
|                 | or Un |       |       |       |        |        |
|                 | it {# |       |       |       |        | **b    |
|                 | chips |       |       |       |        | lade** |
|                 | -sens |       |       |       |        |        |
|                 | or-un |       |       |       |        |        |
|                 | it .u |       |       |       |        |        |
|                 | nnumb |       |       |       |        |        |
|                 | ered} |       |       |       |        |        |
|                 |       |       |       |       |        |        |
|                 | **(   |       |       |       |        |        |
|                 | Units |       |       |       |        |        |
|                 | n     |       |       |       |        |        |
|                 | eeded |       |       |       |        |        |
|                 | for   |       |       |       |        |        |
|                 | one   |       |       |       |        |        |
|                 | bla   |       |       |       |        |        |
|                 | de)** |       |       |       |        |        |
+-----------------+-------+-------+-------+-------+--------+--------+
|                 | 2     | 5     | 6     | 8     | 10     |        |
|                 | chips | chips | chips | chips | chips  |        |
|                 |       |       |       |       |        |        |
|                 | \(1\) | \(1\) | \(2\) | \(2\) | \(1\)  |        |
+-----------------+-------+-------+-------+-------+--------+--------+
| 150 (r) x 150   | 5406  | 13356 | 15808 | 21008 | 26208  | 118602 |
| (*rϕ*)          |       |       |       |       |        |        |
|                 | \-    | \-    | 304   | 404   | 504    | 1920   |
| 225 (r) x 150   |       |       |       |       |        |        |
| (*rϕ*)          | 106   | 424   | 416   | 624   | 832    | 3442   |
|                 |       |       |       |       |        |        |
| 150 (r) x 300   | \-    | \-    | 8     | 12    | 16     | 56     |
| (*rϕ*)          |       |       |       |       |        |        |
|                 |       |       |       |       |        |        |
| 225 (r) x 300   |       |       |       |       |        |        |
| (*rϕ*)          |       |       |       |       |        |        |
+-----------------+-------+-------+-------+-------+--------+--------+

## Table 1. Number and sizes of Pixel cells on a Blade {#table-1.-number-and-sizes-of-pixel-cells-on-a-blade .unnumbered}

+------------------+-----------------+---------------+----------------+
| **Columns**      | **Sensors /**   | **(*rϕ*)**    | ***r***        |
|                  |                 |               |                |
| **x rows**       | **blade**       | **\[cm\]**    | **\[cm\]**     |
+------------------+-----------------+---------------+----------------+
| 2 x 1            | 1               | 1.730         | 0.935          |
|                  |                 |               |                |
| 3 x 2            | 2               | 2.540         | 1.745          |
|                  |                 |               |                |
| 4 x 2            | 2               | 3.350         | 1.745          |
|                  |                 |               |                |
| 5 x 2            | 1               | 4.160         | 1.745          |
|                  |                 |               |                |
| 5 x 1            | 1               | 4.160         | 0.935          |
+------------------+-----------------+---------------+----------------+

## Table 2. Outside Dimensions Sensors {#table-2.-outside-dimensions-sensors .unnumbered}

+--------+---------+--------+---------+--------+---------+---------+
| **z**  | #       | **Bl   | **S     | **C    | **P     | *       |
|        | Radius  | ades** | ensor** | hips** | ixels** | *Area** |
| **cm** | {#radiu |        |         |        |         |         |
|        | s .unnu |        | **Mo    |        |         | *       |
|        | mbered} |        | dules** |        |         | *m^2^** |
|        |         |        |         |        |         |         |
|        | **mm**  |        |         |        |         |         |
+--------+---------+--------+---------+--------+---------+---------+
| ± 32.5 | 60 -    | 24     | 7       | 1080   | 3.0 x   | 0.07    |
|        | 150     |        |         |        | 10^6^   |         |
+--------+---------+--------+---------+--------+---------+---------+
| ± 46.5 | 60 -    | 24     | 7       | 1080   | 3.0 x   | 0.07    |
|        | 150     |        |         |        | 10^6^   |         |
+--------+---------+--------+---------+--------+---------+---------+

## Table 3. Parameters of the CMS pixels End Disks.  {#table-3.-parameters-of-the-cms-pixels-end-disks. .unnumbered}

+--------------------------------------------------------+-------------+
|                                                        | #           |
|                                                        | ### 4 Disks |
+--------------------------------------------------------+-------------+
| Number of readout chips                                | 4320        |
|                                                        |             |
| Luminosity *L* = 10^34^ cm^-2^ s^-1^                   | 1.0         |
|                                                        |             |
| Average number of hit pixels per chip                  | 0.52        |
|                                                        |             |
| Number of transmitted signals per hit pixel            | 10          |
|                                                        |             |
| Average number of signals per chip per event           | 5.2         |
|                                                        |             |
| Chips per link                                         | 3 - 9       |
|                                                        |             |
| Average data rate per link \[MHz\]                     | 2.1         |
|                                                        |             |
| Number of links                                        | 768         |
|                                                        |             |
| Number of FEDs                                         | 12          |
+--------------------------------------------------------+-------------+

## Table 4. Data rates in the Forward Pixel. {#table-4.-data-rates-in-the-forward-pixel. .unnumbered}

![](media/image46.png)

Figure 1. Layout of sensors, in region Figure 2. P-stop rings around

of two neighboring Readout Chips. n+-type pixels.

![](media/image48.png){width="3.9972222222222222in"
height="4.178472222222222in"}

Figure 3. Dimensions of the Blade and position of the sensors.

![](media/image49.png){width="6.5in" height="5.455555555555556in"}

![](media/image50.png){width="3.092361111111111in"
height="2.3805555555555555in"}

**f**

2.  **Common Projects (CP)**

    **1.6.1 Barrel Yoke and Vacuum Tank**

    The US CMS is responsible for payment to the barrel yoke contract.
    There is no procurement, or supervision responsibility.
    Nevertheless, the FEA for the loading of the vacuum tank by the
    inner detectors, notably HCAL, was performed by Fermilab. Indeed,
    the vacuum tank was redesigned on the basis of this study and
    considerably strengthened. In addition, the rails which hold the
    HCAL are part of the vacuum tank. These rails were designed by the
    HCAL engineering team, and the through weld technique, again leading
    to an improved safety margin, was specified by that team. The rail
    FEA was also performed by the HCAL engineering design team.

    **1.6.2 Superconductor, Pure Aluminum and Aluminum Stabilizer**

    The US CMS Project is responsible for the procurement and
    supervision of the order for the superconductor strand, the ultra
    pure aluminum and the bulk aluminum for the magnet coil. This effort
    involves specification of the materials, creating the bid package,
    evaluating the bids, awarding the contract, and later vendor
    supervision. Responsibility for this effort resides at Fermilab,
    with R. P. Smith taking the leading role.

    **1.6.3 Endcap Yoke**

    **1.6.3.1 Introduction**

    The CMS endcaps, located at each end of the detector, consist of 3
    large diameter iron disks (YE1, YE2, and YE3) and 1 smaller diameter
    (nose) disk mounted axially along the beam line. The primary
    function of these endcaps is to return the large magnetic flux from
    the 4 Tesla field by concentrating it within the iron. These endcap
    disks provide mechanical support for the CMS endcap muon system. The
    large quantity of iron in these disks also acts as an absorber to
    filter out the hadronic backgrounds. Table 1 shows the sizes and
    weights of each disk.

  ------------------------ ----------- ----------- ----------- -----------
  Iron element             YE1         nose        YE2         YE3

  Outer radius (mm)        6955        2630        6955        6955

  Inner radius (mm)        975         1000        950         1040

  Thickness (mm)           600         920         600         250

  Weight (tons)            721         144         721         300
  ------------------------ ----------- ----------- ----------- -----------

Table 1. Geometry of the endcap disks.

In order to provide access to the CMS detector elements, each endcap
must move axially. Each disk is mounted on a cart which moves on four
air pads. Hence each disk can move independently of the other disks.
When assembled as an endcap the disks are connected at the outer
perimeter and have spacer rings providing support at the inner radius.
The entire endcap is supported on the barrel yoke by the Z-supports
which are located at a radius of roughly 4750mm.

An important design question for the endcap yoke is the large 4 tesla
magnetic field. Such a field creates large magnetic forces on the disks
which are listed in Table 2. The ratio of magnetic force to weight for
the first disk, YE1, shows a static magnetic force equivalent to an
acceleration of roughly 8 G's. These large forces act to deflect the
disks toward the CMS interaction point. Our calculations indicate a
maximum deflection of roughly 14mm when the field is energized. The
amount of deflection depends critically on the preload provided by the
Superbolts in the disk assembly. The overall design of the endcap disks
is greatly influenced by the magnetic loads.

  -------------- ---- ----------------- --------------------- -----------------
  element             Magnetic force    Magnetic force        Weight (tonnes)
                      (MN)              (tonnes)              

  YE1 + nose     61                     6200                  865

  YE2            17                     1700                  721

  YE3            2                      150                   300
  -------------- ---- ----------------- --------------------- -----------------

Table 2. Endcap magnetic forces.

The US/CMS Project is responsible for the design of the endcap iron, the
supervision of both manufacture and assembly at CERN as part of the US
contribution to the CMS Common Projects. The US/CMS is also responsible
for much of the procurement of these items. The specific
responsibilities are elaborated in each section.

**1.6.3.2 YE1 disk**

The YE1 disk is composed of 20 roughly equal trapezoidal blocks each
weighing about 35 tonnes. The blocks are bolted together using
Superbolts (see section 1.6.2.8). Each block has 9 concentric rings of
Superbolts, each at a different radius, connecting it at each
interfacing surface. When the magnetic field is activated the disk will
dish in toward the IP. As a result, on the face away from the IP the
surfaces are in compression; the side toward the IP will be in tension.
Of course, the Superbolts must provide sufficient preload that all
surfaces are in compression. In order to provide additional stability
there are inner rings of high strength steel on both the interior
(toward the IP) and exterior faces.

The steel blocks are made of low carbon steel with a yield strength of
at least 250 MPa. The relative permeability must be at least 140 at an
induced field of 1.8 tesla, and the uniformity of permeability within
one disk must be less than 5% at an induced field of 1.8 tesla. The
blocks are 600mm thick (for YE1 and YE2) and 250mm thick for YE3. These
blocks may be rolled or forged as long as they meet the specifications
stated above.

The interfacing surfaces (where the Superbolts tie the blocks together)
are machined. Other surfaces do not need to be machined but they must
meet the overall tolerances for the disk. The tolerances for the disks
are stated for the assembled disks and not for individual blocks. The
manufacturer must insure that the block tolerances are sufficient that
when assembled into a complete disk, the tolerances are achieved.

Mounted to the front face of YE1 are two large nose disks (YN1 and YN2)
and a very large (300-tonne) forward calorimeter which will be
cantilevered from YE1. The anchor points for the supporting struts are
placed as high as possible (blocks 12 and 16) on YE1 because of this
large cantilevered load.

On the tension and compression faces of YE1 there will be a number of
additional holes for interfacing to other elements or subsystems of CMS.
On the tension side of YE1 there will be holes for (1) the Z-supports
(mechanical support for the endcaps), (2) the mounts for the cathode
strip muon chambers, (3) the outer connections (see Section 1.6.2.9)
which tie the disks together and to the barrel rings. Drawings exist to
locate and specify all these holes. Table 4 gives a list of the hole
drawings for YE1.

3.  **YE2 disk**

The YE2 disk is very similar to the YE1 disk; all material
specifications are identical. However, since the magnetic forces are
much less there are fewer Superbolts required. There are only 6
concentric rings of Superbolts in YE2 (compared to 9 rings in YE1). In
addition, since there is no cantilevered load on YE2, the anchor points
for the supporting struts are placed at a lower height (blocks 13 and
17) instead of the YE1 location (blocks 12 and 16). There will be two
YE2 disks, one for each endcap of the CMS detector.

4.  **YE3 disk**

The YE3 disk is also very similar to the YE1 disk; all material
specifications are identical. YE3, however, is only 250mm thick. Once
again, since the magnetic forces are much less there are fewer
Superbolts required. There are only 3 concentric rings of Superbolts in
YE3 (compared to 9 rings in YE1). Furthermore, since YE3 is only 250mm
thick these Superbolts cannot fit at the same radius on both the tension
and compression side so the locations are offset. The anchor points for
the supporting struts are placed at the same height as in YE2 (blocks 13
and 17).

**1.6.3.5 Endcap Nose (YN1 and YN2) and HE connection**

The endcap nose disks YN1 and YN2 provide mechanical support for the
large cantilevered load of the forward calorimeter (HE) as well as
shaping the magnetic field for the endcap muon chambers. Both YN1 and
YN2 are supported on the nose support tube as shown and attached to the
YE1 disk with large tie rods. The YN1 disk has 6  slots machined for
the alignment passages located at z -- 6635. The YN1 disk also has
machined connections at the outer radius for the five HE connection
brackets per endcap.

Because the magnetic forces in this area are very large, the HE
connection has been designed with a slip joint. As the YE1 disk deflects
it exerts a force couple on the HE; tension at the outer edge (R = 2700)
and compression at the inner edge (R = 775). A slip joint at R = 775
decreases the compression force on HE and prevents any bending moment on
the back face of HE

As a result of the alignment passages the two endcaps will not be
identical. Both YN1 and the nose support tube will be different on each
endcap, and separate drawings are specified.

**1.6.3.6 Endcap Carts (YE1, YE2, YE3)**

Each disk is supported permanently on a large steel cart structure which
is also used for moving the disks. These carts are made from a steel
weldment, two strut assemblies, and one hinge-keel mechanism. The carts
are each supported by four air pads which typically have a 250-tonne
capacity. The air pads for the YE1 cart will have a capacity of at least
350-tonne each because of the higher loads on YE1. The expected weight
of a fully loaded YE1 cart is 1375 tonnes. Since the experimental floor
is inclined at 1.3% slope, the center of gravity for the +z and --z
carts will be different so the location points for the air pads will
also be different.. Whenever the magnet is energized the carts will rest
on grease pads which have a horizontal motion. Hence the +z and --z
carts will have a slightly different location for the grease pads.

The hinge mechanism is necessary because as the magnet is energized and
the disks bend, the support point must be free to rotate. The struts
keep the disk in the vertical position and are used to adjust the
attitude of the disks by changing the length. The keel mechanism is a
fail-safe device and is intended to keep the disk from falling in case
of a total strut failure.

The struts are made from a hollow tube which is attached on both ends to
threaded parts with a pair of spherical thrust washers and a pair of
nuts. The washers are arranged to make a spherical joint at each end of
the strut. Hence the strut length, and thus the disk attitude, can be
controlled from either end of the strut.

The hinge for each disk is made in two parts on either side of the keel.
The hinge is bolted to the bottom of the disk and to the top of the cart
weldment. The keel is a plate attached to the bottom of the disk and is
suspended inside a rectangular hole in the cart weldment.

The cart weldments are mostly made from 100mm plate steel. The yield
strength of the steel plate must be 240 MPa, which is structural quality
steel ASTM A36 or equivalent. Two endcaps are required, items in table
are per endcap.

The YE3 cart is quite different from the others . The disk is lighter so
the hinges are smaller and located farther from the beam line. The YE3
cart must be designed to carry a large shielding wall behind the ME4
muon station chambers. This wall will not be present at the beginning of
CMS so the center of gravity will change by a substantial amount.

CERN has made a preliminary agreement with the Chinese Academy of
Sciences that the CAS and CERN will provide funding for the procurement
of all the endcap carts. US CMS will have the technical responsibility
for supervision of production and acceptance of the carts.

**1.6.3.7 Endcap Spacer Rings and Endcap Wall**

The spacer rings span the distance between the endcap disks in the
closed position. Each ring is permanently attached to one disk by
bolting to the center ring on the compression side of the disk. These
rings carry the magnetic flux to disks YE2 and YE3. Because of this
magnetic flux these disks deflect enough that the spacer rings remain in
compression while the field is energized. Thus the spacer rings carry
forces between the disks. These spacer rings also provide shielding for
the muon chambers mounted on the faces of the disks.

the alignment lines for the muon chambers pass through slots machined in
these spacer rings. Due to the asymmetry of the alignment system the +z
endcap rings will be different from the --z endcap rings.

8.  **Superbolts**

The Superbolts are large (M72) bolts for the assembly of all the disks.
These bolts allow a significant and well-defined preload to hold the
blocks together under the large magnetic forces.. Once the disk has been
assembled and preloaded, these machined cavities are closed with fill
blocks tack welded into place. The right side of Fig. 14 shows the 12
M16?? Bolts used to tighten (preload) the Superbolt.

9.  **Disk Connection**

Each of the disks must be supported at the inner and outer edges against
the large magnetic forces. On the inside edge the spacer rings perform
this function. On the outside edge the disks are separated by posts. The
disk itself is a dodecagon (12-sided) so the post assemblies are located
at each of the twelve points of the dodecagon. In order to maximize the
space for muon chambers each post assembly contains two small posts
rather than one large one. These connections tie together not only YE1,
YE2, and YE3 but they also tie YE1 to the barrel iron yoke.

Each post contains a spherical bearing to minimize stresses due to
location tolerances for the disks and the bending motion of the disks
under magnetic loading. At four post assembly locations per disk there
is a hydraulic jack which connects the two disks and is used to pull
them together tightly prior to energizing the magnetic field. These
jacks can also push them apart for disassembly and maintenance.

[^1]: The rest 216 (+8) smaller chambers will be assembled at PNPI
    (St.Petersburg) and IHEP (Beijing). Chamber parts and electronics
    (full assembly kits) and critical tooling are provided by the US.
    Standard assembly and testing procedures developed in the US will be
    used to assure the quality control. Assembly labor for these
    chambers is paid by Russia and China as their contribution to CMS.

[^2]: *General Electric Co.*, Coshocton, Ohio 43812, USA

[^3]: *Plascore, Inc.*, Zeeland, Michigan 49464, USA

[^4]: The CSC Sector Receiver delivers 12 bits of φ information per 60°
    derived from the LCT bit pattern, which corresponds to 24576 bins in
    φ. It also delivers 11 bits of η information, or 2048 bins. The DT
    trigger server delivers 11 bits of φ information per 30°, giving
    24576 bins in φ. It also delivers 5 bits of η information per wheel,
    which is 80 bins in η for half of the barrel.