1. R. Denz, TE-MPE-EP Acknowledgements: J. Steckert
Quench Detection Systems for the Next Generation of Accelerator Magnets
R. Denz, TE-MPE-EP
Acknowledgements: J. Steckert

2. Introduction & motivation
Classical superconducting NbTi based accelerator magnets can normally be protected with a fixed set of detection settings allowing as well the use of robust but less flexible technology such as analog bridge detectors.
Example MB and MQ protection in LHC
In case saturation effects are significant, also classical magnets may require dynamic, current depending detection settings especially in case of limited instrumentation. This approach normally requires the use of a digital detection system. In addition such a system needs a dedicated current sensor.
Example 600 A corrector magnet circuit protection in LHC
Future Nb3Sn based accelerator magnets by default require dynamic detection settings in order to cope with the specific physics of these magnets.
Implementation of this functionality requires a digital system
Required user input: threshold voltages, maximum permitted reaction times …
Base on past experience it is strongly recommended to develop and test the quench detection systems at an early stage of the magnet testing (as planned now )

3. Digital quench detection systems
The first deployment of digital quench detection systems based on micro-processors dates meanwhile 30 years back (R. Flora et FNAL 1982)
The majority of the LHC quench detection systems are digital
Digital systems provide functionalities, which cannot be realized with classical electronics
Examples are the protection of 600 A corrector magnet circuits and the aperture symmetric quench protection for LHC main magnets MB and MQ
Digital quench detection systems are actually mixed signal systems, where the final decision whether a signal is regarded as a quench or not is taken by a micro-controller or processor, a digital signal processor DSP or in more recent developments by a field programmable gate array FPGA.
Detection algorithm is implemented in the device firmware  computer code typically written in C, VHDL (not a programming but a hardware description language)
Basic construction elements are the analog input stage, the analog to digital converter, the digital core and the interfaces to interlocks and supervision.
The isolation barrier in modern systems is always in the digital signal path.
Supersedes designs based on isolation amplifiers

4. Detection systems for Nb3Sn magnets
Proposed solution is a multi-channel digital detection system
Two magnet voltages + current
Dedicated current sensor required; for accelerator operation this sensor should be redundant (detection system by itself is always redundant)
Systems for inner triplet upgrade can be installed in radiation free areas (relocation of present protection systems during LS1)
Multi-channel digital detection systems are already used in the LHC for the aperture symmetric quench detection of the LHC main magnets (type DQQDS)
System has four isolated input channels and can be easily re-configured
System configuration can be change remotely
Exploitation requires dedicated supervision application
Default for LHC, to be adapted for test bench

5. Test & deployment strategy
As agreed recently QPS will start the deployment of the first digital detection systems for Nb3Sn magnets beginning of 2013 (project engineer in charge is J. Steckert)
In the initial phase system will be installed in parallel to the existing systems and be adapted to the respective interlocks
A supervision application for the new detection system will be delivered and the test bench operators will be trained accordingly
On the mid term the system must be upgraded to an LHC like configuration
Separation of protection functionality from test bench DAQ systems
Installation of a powering interlock controller (PIC)
In collaboration with TE-MPE-MS, M. Zerlauth
Deployment of full PIC and QPS supervision layer
Timescale to be verified as there are potential conflicts with LS1 activities