# Presentation: 071576

## Towards a Detector Control System for the ATLAS Pixeldetector

- Susanne Kersten, University of Wuppertal
- Pixel2002, Carmel September 2002
- Overview of the Detector Control System
- The Front End System
- The Back End System
- Experience with the Testbeam Setup
- Summary and Outlook

**Notes:**
As there are several talks about the ATLAS pixeldetector, i would like to refer to these talks and begin
Directly with an overview of the detec...

## Tasks of the DCS

- Guarantee reliable data taking + safe operation of the detector
-             **** Monitoring and control of hardware
-             **** User interfaces for experts and shifters
-             - Reaction to error conditions and error reporting
-             - Histograms for trend analysis
-             - Communication to Data Acquisition System .....
-  + Our detector specific constraints:
-              - high power density
-              - harsh radiation environment
-              - inaccessibility over long terms

**Notes:**
For the beginning now we concentrated on choice and development of hardware
And the user interface, so that we have a system which can already be operated during testbeam or system tests
How should our system look like

## Overview of Pixel-DCS 

**Notes:**
ATLAS DCS organized hierarchically in 3 levels: controlroom with atlas central station
Counitng room with local control stations of each subdetector
 and in the atalas cavern and detector mainly the hardware, the io-units, the front end system
Which is the counterpart to the backend system build by local and central control station
And the software running on them
Logical structure backend-frontend
Beschraenke mich im wesentlichn auf folgende hardware components

## Front End System

## Power Supplies 

- depletion voltage for the sensor
- two low voltages for the front end electronics
- three low voltages for the optolink
- Grounding and redundancy considerations  high granularity
-      ca. 4000 power supply channels
- High level of local intelligence
- Operation of channel groups
- Support interlock system

**Notes:**
Complex system requires high level of local intelligence, able to react to error conditions by ist own!
enhances safety of detector
and reduces network traffic
2 module/per power supply

## Evaporative Cooling System

- Ca. 20 kW total power dissipation must be removed
- minimal extra material in the tracker sensitive volume
- using C3F8
- non-flammable
- non-conductive
- radiation resistant
- Detector can be cooled
- down to –6 °C
- Prototype at CERN:

**Notes:**
Power density: 0.7 W/cm2
flow  rates 1/20   those in a monophase liquid system
large scale (6 KW) prototype  circulator built
Structures to be cooled, compressor, tank and their control and input output regulators
erconnecting tubing is replicating length and hydrostatic heat differences as expected in final system

Smallest unit 2 staves: parallel cooling circuit
supplies up to 25 parallel cooling circuits (1/4 of detector)  
interconnecting tubing replicating the lengths and  hydrostatic heat differences expected in the final installation in the ATLAS cavern:

## Embedded Local Monitor Box

- General purpose front end IO device developed by ATLAS DCS group
- 64 ADC channels 16 bit
- 34 digital IO lines
- Radiation tolerant
- CAN serial fieldbus
- CANopen protocol
- Pixel: ca. 250 ELMB
- Design of CAN-fieldbus System ?

**Notes:**
Can fieldbus specially suitable for widely spread applications, 120m expected for pixels
Canopen protocol standardizes datastructure and communication
everal hundred XXX of elmbs will be used, how control them?
Design of CANBus distribution

## Thermal Interlock System

- Aim: protect detector modules
- against risks associated with
- de-lamination
- latch ups
- failure in cooling system
- NTC resistor on each detector
- standard monitoring
- hardwired Interlock-Box
- Logic Unit: combine signals
-      opto couplers, allow pattern monitoring

## The Interlock Box

- Robust solution! Not relying on any software!
- 2 bit logic:
-      temperature too high,
-      temp too low,
-      broken cable, short circuit
- Overall max. error: 1K
- Operation in radiation environment:
-    5 x 10 11 n/cm2
-    93 Gy

- i

**Notes:**
Signal from the NTC compared to
threshold, excessive deviation
creates logical signal
Overall error includes error of electrical circuit, ntc and cables

## Mapping between Hardware components and Software

- Motivation: graphical surface,
-      make problems evident,
-      easy problem tracing
- _Geographically oriented tree structure_
- Level 1: pixeldetector
- Level 2: shells and disks
- Level 3: parallel cooling circuits
- Level 4: Base Detector Unit

## Back End System

## Supervisory Control And Data Acquisition System: PVSS

- Commercial product PVSSII from ETM, Austria
- LHC wide decision
- Can be distributed over many stations
- Flexible and open architecture
- Basic functions for automatisation
- Standardized interface to the hardware
- Application programming interfaces

## Datapoints 

- Basic properties defined by the dp type
- Dp = logically related process variable
- Individual configuration attributes in dp
- configuration, reaction, GUI via scripts

**Notes:**
Ist concept is based on datapoints
Jeder datapoint hat dp-elements, dpelement kann weitere sub-dp-elements haben usw.. Baumstruktzr
Unterste ebene nennt man blaetter
‚common‘or ‚lock‘ data point or data point elements attributes

## OPC server

- Connection between PVSS and CAN nodes via OPC server
- OLE for Process Control
- Based on Microsoft object
- Model DCOM/ COM
- Industrial standard interface
- No specific driver for each client

**Notes:**
How do you get physical data into your scada system, take the opc server 

COM: component object model
DCOM: distributed com
Ole: object linking and embedding

## Testbeam Setup

## Aims and Questions

- Support shifter with information
- Experience with PVSS, are our needs covered by the program
- Temperature behaviour of detector module
- System test for thermal interlock system
- DCS and DAQ together
- Build a system which can be used for performance tests (operating parameters ..)
- Build a system which can easily be expanded
- create basis for hierarchical structure - BDU

**Notes:**
Make a system which uses the datapoint cncept in an efficient way!

## Testbeam DCS Setup

**Notes:**
Setup as planed for final installation, in so far a system test for thermal interlock system as well
Power, signal and canbus: cable orginal length

## PVSS Startpanel 

- For DCS Operator
-      - apparatus oriented -
- For Shifter
-      - geographical or application oriented -

**Notes:**
Testbeam setup 3 parts,  
 config pvss Config hardware Monitroing of the devices

## Prepare PVSS

- Start panel

**Notes:**
If necessary one can create new data point types, during initialisation
It is checked whether all data point types are available

The data points, wich structure is defined by the data point types, will be created here
Create and set elmb, further can be added, see table (reference name, pvss internal addressing

‚Cabling‘ zwischen opc server und datapoints in vss via create & set canbus und create&set elmb
Cabling between hardware and userpanels via „create&set tbcoolingbox“usw

Alert handlind is pvss intern, attributs of dp must be canged
Software interlock: wert von datapunkt, die per datapoint function verarbeitet wird

## Configure the Hardware

**Notes:**
Config can bus synch interval setzen, network starten, reset usw
Elmb gain, rate, type, ntm of indivudaul elmb!
Voltages sieht man!
Digital input output register    Portc dig out   Port f input   Port in/out
One can see calib factor in use
Calibration possible, factors are used in actual project, factor can be imported or exported

## Operation Parameters for ADC and CAN-Bus

- No operation close to the limits!
- max. noise of ADC
-  Conversion rate:
-             61.6 Hz
-  Synch Interval:
-             5 sec
- Bus speed:
-             125 kBit/sec

**Notes:**
Adc messung: max fehler, 50 min alle 5 sec, fuer 64 kanaele
2mV correspond to 0.1K

## Monitoring: Cooling Box

**Notes:**
Location of sensors in the cooling box is visualized, observe the temp gradient in the box

## Monitoring: Base Detector Unit

**Notes:**
2 pccs are actual created, scaling to larger system easy, more PCC, 
more parameters can be added to bdu 
For the moment software interlock can be seen,  actual temp
Actual level for software interlock usw are shown

## Temperature Behaviour of a Detector Module

- @ Environ.Temp of  24 C
- T  8 K
- with an active front end electronics

**Notes:**
2 different elmbs

## Summary and Outlook

- Complete chain for thermal interlock system 
- Long cable no problem, no cross talk DAQ – DCS 
- PVSS covers our needs
- Vision manager  instable
- trending pure   seperate tool for histograming
- We now have a system
- for further DCS system studies (several CAN Busses, ...)
- where further quantities (LV, HV..) can easily be added
- which can be used for the control of larger detector parts

**Notes:**
Where further quantitties can easily be added to the base det. Unit
Larger det parts be controlled by increasing the tree structure