LHCb 2003-121

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					                                                                          LHCb 2012-121
                                                                                       CALO
                                                                          8 December 2012




Cards, Crates and Connections
      for the Calorimeters


                        David Gascon, Sonia Luengo
                               Universitad de Barcelona

              Gérard Bohner, Rémi Cornat, Pascal Perret
               Laboratoire de Physique Corpusculaire, Clermont-Ferrand

       Christophe Beigbeder, Dominique Breton, Olivier Callot,
               Jacques Lefrançois, Frédéric Machefert
                     Laboratoire de l’Accélérateur Linéaire - Orsay




                                   ABSTRACT

  This note summarizes the result of several discussions on the details of the electronics
  implementation on the platform of the calorimeters. It contains an update on already published
  information, and precision on the crate layout and cabling.
Page 2                  “Cards, Crates and Connections for the Calorimeters”              LHCb 2012-121




1 Cell numbering

         The official calorimeter cell numbering scheme was discussed several years ago, and partially
         described in some notes[1][2], but has been slightly modified since. The current, official version
         is given here.

         Each cell is labelled with a 16-bit cell-ID, which contains 4 fields



         Calo-ID (2b)      Area (2b)               Row (6b)                          Column (6b)



                The low order 6 bits contain the column number, increasing with the X coordinate.

                The next 6 bits contain the row number, increasing with the Y coordinate.

                The next 2 bits the area: 0 for outer, increasing towards centre.

                The upper 2 bits are the detector number, in the order SPD, PreShower, ECAL, and
                 HCAL. This last field of the numbering may be absent online, as the type of calorimeter is
                 known by the bank the cell is in. However, if we have 16 bits, the full ID is encouraged.
                 This will be the case in the readout, but probably not in the L0 trigger.

         The Row and Column numbering is centred on the beam line. For SPD, PreShower and ECAL,
         the beam line is between Row and Column 31 and 32, for HCAL this is between Row and
         Column 15 and 16.

         As the LHCb system is direct, a 2-D view of the calorimeter, with X increasing towards the right
         and Y increasing towards the top, means that the calorimeter is seen from the Muon, looking
         towards the Velo, i.e. this is the view when being of the PM side of ECAL/HCAL.


2 Crate layout

         The layout of the cards in the crates has been described in a note[3]. It has been discovered since
         that the Figure 2 of this note was incorrect. In the mean time, the work on the readout of the
         calorimeter has pushed us to centre a bit more the cards in the crates, changing slightly the HCAL
         layout. The corrected figures are given in this note, which supersedes the note 2002-015. Note
         that ‘Right’ and ‘Left’ are defined when looking at the detector from the PM side towards the
         VELO, opposite to the Z axis, so that X (and the cell number) increases from left to right and Y
         from bottom to top.
LHCb 2012-121                 “Cards, Crates and Connections for the Calorimeters”                                                                Page 3


2.1 ECAL

                   14              14                12                   16
                                                                                  2 3    4     5 6 7 8    9 10 11 12    13 14          Crates 1 and 2
                   13              13                11                   15


                   12              12
                                                      3
                                                     10                   14


                   11              11                 9                   13    1 2 3 4        5 6 7 8    9 10 11 12    13 14 15 16    Crate 3

                                            12       12        14         16
                   10              10
                                            11       11        13         15
                                            10       10   14     11        14
                   9                   9                  13     10        13
                                             9        9   12      9        12                                                          Crates 4 and 5
                                                                                    3 4        5 6 7 8    9 10 11 12    13 14 15 16
                                             8        8   11      8
             1     8
                              2        8   47         7
                                                          10
                                                           9
                                                          68
                                                                77
                                                                  6
                                             6        6           5        5
                   7                   7
                                             5        5
                                                           7      4       64
                                                           6      3         3
                                             4        4        14          16
                   6                   6
                                             3
                                                 5    3        4
                                                               13          15
                                                                                    3 4        5 6 7 8    9 10 11 12    13 14          Crate 6


                   5                   5              4                    8
                                                                                          No neighbours

                   4                   4              3                    7


                   3                   3
                                                      3
                                                      2                    6
                                                                                    3 4        5 6 7 8    9 10 11 12    13 14          Crate 7



                   2                   2              1                    5        Validation       CROC        Validation
                                                                                      Card                         Card



                                                                      ECAL Left
                  12              16             14                 14
                                                                                    3 4        5 6 7 8    9 10 11 12   13 14          Crate 8
                  11              15             13                 13

                   12
                  10              14             12                 12
                                                                                                                         No neighbours


                   9              13             11                 11              3 4        5 6 7 8    9 10 11 12   13 14          Crate 9

            2      4     14       14
                                                 10                 10
            1     3    1113       13
          14 11 14       12       12
          13 10 13                               9                    9
          12   9 12      11       11                                                                                                  Crates 10 and 11
                                                                                1 2 3 4        5 6 7 8    9 10 11 12   13 14
             9 8 11      10
               7 10
                          9
                            1010
                               9           13    8
                                                          14          8
               68 9
          5    5   8      8        8
         84 4 7           7        7
                                                 7                    7
          3    3   6
             2    4       6        6                                                                                                  Crate 12
                                                                                1 2 3 4        5 6 7 8    9 10 11 12   13 14 15 16
            1   10 3      5        5
                                                 6                    6


                   4               8             5                    5


                   3               7             4                    4


                   2
                        12         6             3                    3
                                                                                  2 3     4    5 6 7 8    9 10 11 12   13 14          Crates 13 and 14



                   1               5             2                    2                 Validation   CROC       Validation
                                                                                          Card                    Card



                                                                ECAL right
                                                                    Figure 1 : ECAL crates layout
Page 4             “Cards, Crates and Connections for the Calorimeters”                                                                    LHCb 2012-121


2.2 HCAL


                      9                                 13                                  Half filled cards



                                                        12                         3    4     5 6 7 8          9 10 11 12 13                      Crate 1
                      8
                                     8                      15


                                     7                       14              No neighbours
                      7

                                     6                       13

                                                                                2 3 4         5 6 7 8          9 10 11 12       13 14 15          Crate 2
           1          6
                                     5
                                         2             12


                                     4                       11
                                                                                                       CROC
                                     3                       10
                      5
                                     2                          9



                      4                                 11

                                                                                                    HCAL
                      3                                     10




                                                       Figure 2 : HCAL crates layout


2.3 PreShower-SPD

                                                                                       32 channel cards

           8         15         10                     12

                                                                     2 3    4     5 6 7 8          9 10 11 12       13 14 15           Crates 1
                                     2
           7         14          9                     11




                          6     13           14        15                         5 6 7 8          9 10 11 12                          Crates 2
           6         13
                                         8        13    15
                          5     12
                                                        14

           5
               1     12   4   3 11
                                         7
                                         6   4 11
                                                  12                                    No neighbours

                                         5        10
                                                        3
                          3     10                                   2 3    4     5 6 7 8          9 10 11 12       13 14 15           Crates 3
                                         4        9         2
           4        11
                          2      9            7         8
                                                                                        Half filled cards
                                                                                       32 channel cards

           3        10           6                      8

                                                                     2 3    4     5 6 7 8          9 10 11 12       13 14 15           Crates 4
                                     2
           2          9
                                 5                      7
                                                                        SPD control          CROC           SPD control

                                                                    : '32 channel' means only 4x8 cells, but neighbors on both sides



                                         PreShower + SPD
                                              Figure 3 : PreShower crates layout
LHCb 2012-121           “Cards, Crates and Connections for the Calorimeters”                          Page 5




3 Numbering inside a card

        When processing the signal from a cell, the Front-End electronics handles each channel
        independently, so the order seems completely irrelevant. Except if there is some constraints from
        the cabling point of view. However, we need to define the geometry for computing the sum of 2x2
        cells for the L0 trigger application. We need also to identify the cells corresponding to the 2x2
        candidate, such that PreShower, ECAL and HCAL speak the same language.


3.1 Labelling the 2x2 cluster

        By convention, we identify the group of 2x2 cells by its cell with the lowest row and the lowest
        column number, which is equivalent to the smallest X and Y coordinate. In order that a
        candidate comes from the card where its ‘master’ cell is readout, the neighbours are received
        from higher X or Y locations, and sent to lower X or Y location. With the card numbered as in
        Section 2 , this means that in a crate the neighbours are received from the right in the crate, and
        sent to the left: Neighbouring cards have a slot number higher if they are at higher Y. For the
        connections between crates, for example for ECAL Left, crate 2 receives from crate 3 and sends
        to crate 1.


3.2 ECAL/HCAL card

        The input for the ECAL/HCAL card will be 4 connectors with 8 signals each. One natural choice
        is that these 8 signals come from a row, as a card covers 4 rows of 8 cells. But the constraints of
        cabling in ECAL, where cables have to be laid down and glued on steel tapes running vertically at
        the boundary between hardware modules, impose a cabling where a group of 8 cables on the same
        connector are in fact 2 columns of 4 cells. Inside each the connector, the cells are in increasing
        cell number. The result is summarized in the sketch below.

                3   7 11 15 19 23 27 31
                                                                                                31
                2   6 10 14 18 22 26 30
                1   5    9 13 17 21 25 29
                0   4    8 12 16 20 24 28




                                                                                                0


        This means that the inputs are numbered from bottom to top on the front panel of the card. The
        data labelled 0, 4, 8, 12, 16, 20, 24 and 28 are sent (on the backplane) to the card to the left in the
        crate. The first four signals (0-3) are sent via cable to another card. It should be noted that in
        documents describing the L0 Calorimeter trigger and the neighbours, the received signals were
        named ‘top’ and ‘right’. This is still true as viewed from the cell’s position in the calorimeter, but
        cannot be true at the same time in the electronics crate. However, neighbours are still received
        from the card on the right in the crate. And the top/bottom connection between crates is less
        simple in terms of topology, as described in Section 4 .
Page 6                “Cards, Crates and Connections for the Calorimeters”                         LHCb 2012-121


3.3 PreShower/SPD card

         The PreShower/SPD front-end system is made up of 3 parts: the PreShower very front-end
         receiving the PM signals, the PreShower front-end and the SPD front-end. Since the PreShower
         front-end card processes the trigger data to extract 2x2 clusters, each channel has to be correctly
         mapped to the corresponding detection cell. One has to know how are connected the scintillator
         cells to the very-front end, the very front-end to the front-end and the SPD front-end to the
         PreShower front-end.


3.3.1 PreShower

         The PS scintillator cells mapping on the MAPMT is defined in the note [4]. The connectivity from
         the MAPMT outputs to the front-end input is also defined. The late adaptation in order to take
         into account the scintillator-MAPMT connections will be done directly into the trigger chip on the
         PreShower front-end board (two configurations will be foreseen and user selectable through
         ECS).

         The analogue signals are sent (from very       RJ45 pin #                  Wire color              Pair #
         front-end to front end) onto CAT5e
                                                              1                  White orange
         cables with RJ45 connectors. The                                                                        2
         twisted pairs as well as the connector’s             2                    Orange
         pin-out are numbered in accordance                   3                  White green                     3
         with the TIA/EIA568B standard.                       4                     Blue
                                                                                                                 1
                                                              5                  White Blue
                                                              6                    Green                         3
                                                              7                  White brown
                                                                                                                 4
                                                              8                    Brown




                                                                       1             2             3             4
         On the very front-end board the MAPMT
         channels are grouped by clusters of 4, see               1        2    3        4    5        6    7        8
         nearby figure. The MAPMT output                 A
         numbering correspondence to the PS cells                 9        10   11       12   13       14   15       16
         numbering is quite complex (see Ref. [4]).
         Two horizontal rows correspond to a “PS                  17       18   19       20   21       22   23       24
         element” makes of 4  4 cells read-out by        B
         a bundle of fibers collected into a                      25       26   27       28   29       30   31       32
         connector. A special care has been taken
         in order not to mix channels corresponding               33       34   35       36   37       38   39       40
         to two different PS elements. A PS               C
         element corresponds to 4 analogue very                   41       42   43       44   45       46   47       48
         front-end chips and 4 RJ45. Thus it allows
         a front-end board to be partially filled                 49       50   51       52   53       54   55       56
                                                         D
         without the need to split a cable.
                                                                  57       58   59       60   61       62   63       64
LHCb 2012-121         “Cards, Crates and Connections for the Calorimeters”                           Page 7


        The next tables show the correspondence between the channels and the RJ45 connector and pair.

        Connector A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 C3 C4 D1 D2 D3 D4

          Pair 1      1     3    5     7    17    19   21    23    33   35    37    39   49    51    53   55

          Pair 2      2     4    6     8    18    20   22    24    34   36    38    40   50    52    54   56

          Pair 3      9    11    13    15   25    27   29    31    41   43    45    47   57    59    61   63

          Pair 4     10    12    14    16   26    28   30    32    42   44    46    48   58    60    62   64




3.3.2 SPD

        The 64 SPD data bits are sent on 4 standard Ethernet Cat6 or Cat7 cables using serial LVDS. An
        extra bit indicates the sub-channel, and 5 extra bits allow to inject test patterns on the links. A
        small card will receive these 4 links and put them on the 14 pairs Z-pack hard metric connector of
        the backplane. The pin-out is not defined yet but after a deserialization stage, the data are obtained
        in parallel at 40 MHz. It will become easy to order it into the trigger PGA (HDL code update) as
        soon as the mapping will be known.


4 Racks on the Calorimeter platforms

        There are two platforms to house the electronic racks: The HCAL platform, moving with HCAL,
        and the ECAL platform, moving with ECAL. The PreShower/SPD electronics will be on the
        ECAL platform, the cables between the Very Front End (VFE, near the MAPMT) and the FE
        cards will be long enough to allow opening the ECAL, PreShower or SPD without disconnecting
        any cable. On each side of the detector there are 4 PreShower crates, 7 ECAL crates and 2 HCAL
        crates as indicated in Section 2 . Our current understanding is that the racks should not be too
        high, for compatibility with the Muon gantry, and can contain 3 crates per rack. We need 4 racks
        on the ECAL platform. The location of the crates in the rack should minimise the number of
        cables connecting one rack to the other, and allow shorter cables for those detectors where this is
        the most critical. As the length of the SPD cable is close to the limit of the link technology, we
        decided to put the PreShower crates at the bottom of the racks. Two racks will hold the outer area,
        one rack the middle area, and one rack the inner area. Cable connections exist only between these
        last two racks.
Page 8                 “Cards, Crates and Connections for the Calorimeters”                 LHCb 2012-121


                                                                from HCAL

                                7   7                    8                      6    6                  3   3



                    ECAL 1                                           ECAL 4                  ECAL 6
                    13 cards                                         14 cards                12 cards

                           13                                        2     10                3     9

                    ECAL 2               ECAL 3                      ECAL 5                  ECAL 7
         13 13      13 cards             16 cards      14 14         14 cards       12 12    12 cards
                                    8
                  13       13           16      16               14        14               12     12

                     PRS 1                PRS 2                      PRS 3                   PRS 4
                    14 cards              8 cards                    14 cards                14 cards
                                    4


                                Outer                                Middle                  Inner

            Figure 4 : Proposed rack layout, with the number of cables between various crates

         The order of the rack on the platform should be chosen to minimise the cable length between the
         detector and the FE electronics. For the PreShower and SPD, the longest cables come from the
         centre-bottom MAPMT via the side of the calorimeter. There are inner, middle and outer section
         signals at this farthest location, and this doesn’t give a preferred crate location. ECAL cables are
         coming almost vertically from the PM favouring to have the outer racks near the centre of the
         calorimeter. This configuration is then the default one.


5 Cabling

         The cabling of the Calorimeter platforms has three parts:

                Input signals, coming from the detector. They arrive on the front panel for PreShower,
                 ECAL and HCAL, and on the backplane for SPD. Cable length is critical.

                Interconnection signals, as displayed on Figure 4. These are Ethernet Cat5 cables with
                 RJ45 connectors, plugged on the backplane of the various crates. Most of the cabling will
                 be internal to each rack, except the HCAL-ECAL cables. A small cable tray inside the
                 rack will hold them, at most 70 inside a rack.

                Readout fibres, one or two ribbons per crate, 44 ribbons in total, and trigger fibres, from
                 the Validation (and SPD) Cards to the Selection Crate, up to 16 fibres per ECAL crate, 2
                 fibres per PreShower crate, 208 in total.

         In this section, we try to specify the length and path of the signal and interconnection cables. The
         readout and trigger fibres have almost no length constraint, and should be easy to install.
LHCb 2012-121         “Cards, Crates and Connections for the Calorimeters”                            Page 9


5.1 ECAL signal cables

        The length of the cable can be computed form three parts: The cabling inside the detector up to
        the level of the platform, the cabling in the front part of the rack, and the part in between, allowing
        to reach the proper rack.

        Inside ECAL, the signal cables are attached to steel tapes running vertically. The distance from
        the lowest PM to the platform level thus defines the maximal length. The height of the calorimeter
        is 6.3 m, to which one should add the distance from the last module to the platform.

                                     Inside a rack, the signal cables are attached to cable trays on the side
                                     of each rack, are conducted below the FE card in the space between
                                     two crates, using e.g. a plastic cable tray, and then up to the proper
                                     connector on the card. The maximal length is 1.3 m + 50 cm + 40 cm,
                                     about 2.2 m. One could gain a bit by using the two sides of the rack
                                     for upwards going cables, reducing the intermediate horizontal length,
                                     but this is almost compensated by the length below the platform,
                                     between the detector and the rack.



        The length between the top of the detector and the bottom of the rack is 80cm vertically. One has
        to add also the extra length (24 cm) to go around the beam pipe for the bottom outer cells near the
        centre. In order to be able to move the steel tape, an extra 30 cm is required. Having the outer rack
        near the centre of the platform, the horizontal length is half the half calorimeter width, about 2m.

        With these estimates, and a minimal safety margin, the total length of an ECAL signal cable
        should be 12.0 m.


5.2 HCAL signal cables

        These cables are made of two physical parts, one inside the module, and one from the module side
        to the electronics, with a connector in between. The part inside the module is 4.2m, which is the
        half width of a module. The other part goes along the calorimeter side (6.8 m), below the platform
        towards the rack, which should be as close as possible (1 m) and inside the rack, 1.5 m only as
        there are only 2 crates in the rack. This gives a total of 13.5 m from the PM to the FE card.

        Since the HCAL card is identical to the ECAL card, each 8-coax bundle, corresponding to a
        connector on a card, will receive signals from four different HCAL modules. However at the
        HCAL module side, the coax are also attached by groups of 8 to a multi-coax connector.
        Therefore the HCAL signal cables will be arranged as bundles of 32, which on both side are
        connected to four 8-contact multi-coax connector but the coax have to be arranged in the correct
        order between the two connectors.

        On both side of the HCAL there will be 25 such bundles of 32 coax cables which are about 2cm
        in diameter each. There will be disposed in cable trays running on the side of HCAL Since all
        cables have to be of the same length, the trays will be also used to store the extra length of cable.
        Two trays of 15 cm width and 10cm depth should be sufficient.
Page 10                 “Cards, Crates and Connections for the Calorimeters”                  LHCb 2012-121


5.3 PreShower and SPD cables

          Except the cable between racks (quite short), two types of long cables will be connected on a
          PreShower front-end board: analogue signals from PreShower VFE board and digital data from
          SPD VFE board. Another long cable in the crate is the one connecting the SPD control board to
          the VFE board. There is one cable of each sort for each VFE board, this means 100 of each type.


5.3.1 PreShower signal cables

          17 CAT5e cables (including one for clock and reset signals) will connect a unique very front-end
          board to a unique front-end board. Others configurations are not foreseen except partially cabled
          boards.

          The standard length depends on the part of the detector: 20 m for the lower part and 10 m for the
          upper part.


5.3.2 SPD signal cables

          For the signal cables (SPD VFE -> PS FE) 4 standard Ethernet patch cable (4 pairs cat6 or cat7
          shielded cables) will probably be used. A test of LVDS communication including different kinds
          of cables is in preparation. This test will include compensation for skin effect of long cables, so it
          is delicate and might take 1-2 months from now. The section of each cable will be around 26-28
          mm2.

          The standard length depends on the part of the detector: 20-25 m for the lower part and 10 m for
          the upper part.


5.3.3 SPD control cable

          The same kind of cables will be used for the control connection, from “SPD control board” to
          “SPD VFE card”. The length will be similar.


6 References

             “Calorimeter Data Format and 2-D Zero Suppression Scheme”, O.Callot, LHCb 99-037

             “The readout of the LHCb Calorimeters”, Ch.Beigbeder et al., LHCb 2000-046

             “Cards and Crates layout for the Calorimeter Front-End Electronics”, O.Callot and
                P.Perret, LHCb 2002-015

             “Optical and Electrical Cabling of the PS/SPD”, G. Bohner et al, LHCb 2003-145

				
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