CMS RPC Visualization

3D RPC Chambers display is already implemented in Orca/Oscar using Iguana. We would like to have this RPC visualization available also in a stand-alone program and as a Web interface.

Why and when use a Web interface : in some cases you don't need to do complex manipulation (for example rotating a part of the detector in space), instead you just want to visualize some quantity. In this case a simple Web interface would be easier to develop and use. For example : display of data in the Construction Database. prototype

Why a stand-alone program? I some cases, it is absolutely necessary to work inside Orca, although difficult and slow this can be. Instead there is also the possibility that you want to process a lot of events (for example to sum the signal from many events) and you don't want to run Orca one week to get a single picture. In this case the idea is to run Orca in batch for one week, writing events ready to be displayed on disk and then use a fast stand-alone visualisation program to do the visual analysis. This program will get the detector and event description via XML files. DDD already has XML description of the detector; a similar description will be implemented/used to allow program indipendent transmission of events data between ORCA/Oscar and this visualisation stand-alone program. This format will be used for the "ready to be displayed events".

Objectives Build graphics objects to improve visualization of the RPC chambers.

We need a greater detail: up to the Double Gap.

We want to display information in the Construction Database
Detector layout

RPC(Resistive Plate Chambers) is part of the CMS Muon detector. It is in fact a special purpose detector providing fast information for the Level-1 trigger. Its geometry follows the muon detector geometry. In addition to RPC there are two other types of detectors used for muon identification: Drift Tubes (DT) chambers in the barrel and Cathode Strip Chambers(CSC) in the endcap region.These muon detectors consists of four stations interleaved with the iron return plates. They are arranged in concentric cylinders around the beam line in the barrel region, and in disks perpendicular to the beam line in the endcaps.
So we have a barrel divided in 5 wheels ,12 wedges and 4 stations and two end-caps divided in 4 stations(disks) with rings of 36 or 18 wedges. Stations are numbered 1 to 4 starting from the one nearest to the beam line. In the barrel, we have RPC chambers below each Muon station. MS1 and MS2 will have also RPC chambers on the outer surface.This can be seen in this cross section of an event.
The total number of RPC barrel chambers are 480: all the chambers can be seen in this schematic view that clarifies also why there are 96 chambers for each wheel . Passing the mouse on the chambers you can also see the name of the chamber: this starts with the 3 letter code of the wheel : W-2,W-1,W 0,W+1,W+2 then we have the code of the station: RB1 to RB4 . Then we have in/out for the first two station and finally the indication of the wedge 1 to 12 starting from 3 o' clock going anti clockwise. In case there are two or 4 chambers in the same wedge then we have the following notation:--,-,+,++ . (The CMS reference system has the x axis pointing to LHC center, the y axis pointing up and the z axis along the beam :if we are looking at the LHC having the Jura in front of us, it has the anticlockwise direction.)
All the end-cap rpc chambers have a trapezoidal shape with radial strips. Their number is 540. They are organized in rings and two or more rings form a disk. Each ring contains 36 or 18 chambers (i.e. each chamber sees a sector of 10 or 20 degrees). The first station has three rings of 36 chambers, the other three stations have an outer ring of 36 and an inner ring of 18.
The detector segmentation in z is connected to the level 1 trigger logic. The layer RB2 out is the reference layer and is segmented in three :i.e. each chamber is composed by three double gaps. The other five layers are composed by two double gaps. So we have for the barrel 5*3=15 towers in theta. Each trigger processor sees the zone that connects the center of CMS with a double gap in the reference layer. It sees 2.5 degrees in phi corresponding to 8 strips in the reference layer. This means that we have 144 trigger sectors for each theta tower.The total number of theta towers is 33 with the other 9+9 = 18 towers formed by end-cap rpc chambers.

Tentative list of graphical objects to be developed



Giuseppe Zito:
Last modified .