1. Quench detection electronics for the HL-LHC magnet circuits of the LHC
R. Denz
Acknowledgements:
J. Kopal, E. De Matteis, F. Rodriguez-Mateos, A. Siemko, J. Steckert, G. Willering, D. Wollmann
6th HL-LHC Collaboration Meeting, Paris, November 15th 2016

2. Quench Detection Systems (QDS) for HL-LHC: Introduction
The High Luminosity Upgrade of the LHC (HL-LHC) will increase the already significant diversity in superconducting magnets and circuits
First time (in LHC) use of Nb3Sn based magnets and MgB2 superconducting links
Detection of quenches in Nb3Sn might be a challenge due to the flux jump phenomenon (suppression of spurious system triggers)
Requires as well the development of a new QDS generation including DAQ systems allowing advanced diagnostics
Most of the HL-LHC circuits need active quench detection systems
558 detection systems covering 98 circuits
Number of hardwired interlocks will increase by 5.9% (13440  14228)
QDS design must be highly dependable in order not to compromise LHC operation

3. Quench Detection Systems (QDS) for HL-LHC
IT, D1 and D2 QDS will be installed in HL1 & 5 areas  radiation free
Q4, Q5, Q6 QDS will remain in RR13, RR17, RR53, RR57
can be based on already existing R2E technology
11 T QDS will be installed in RR73 & RR77
HL-LHC will require relocation of existing QDS currently installed in DS areas adjacent to IP1 & IP5 (half cells 8 to 11)

4. QDS for HL-LHC: Basic Ideas
QDS for HL-LHC will be a completely new development based on the experience gained with the LHC QDS so far
In the past dedicated systems had been designed for each type of magnet or superconducting element to ensure optimal quench detection characteristics
Aim of the new designs is a versatile system capable of covering most of the quench detection requirements for the superconducting circuits of the LHC
The new QDS is to a very large extent software-defined
Functional components like filters, voltage comparators or time discriminators are implemented in the device firmware and no longer in hardware

5. QDS for HL-LHC: Conceptual Design
NanoFIP (11 T) / Ethercat™ or PowerLink™ (HL 1/5)
IGLOO2™ (11 T) / Cyclone V or Arria 10™ (HL 1 and 5)

6. QDS for HL-LHC: Kit for Building Quench Detection Systems
Each QDS system is independent and equipped with its own interfaces for interlocks and communication
This approach will require new control interfaces (API), maybe even a more substantial change of the QPS controls architecture, details still to be defined ...
QDS systems will be complimented by DAQ units based on similar design approach e.g. for quench heater circuit supervision
Input channels can be configured individually and signals combined arbitrarily
e.g. one unit can protect 1 x 11 T, 1 x 600 A, 1 x IPQ/IPD etc.
QDS for MgB2 links using differential voltage signals plus magnet voltage
May simplify routing of instrumentation wires  currently under study
Depending on the requirements various configurations can be conceived;
The level of redundancy can be adapted to the actual needs
QPS LHC uses successfully 1oo2, 1oo2 | 1002, all digital systems use internally majority voters (TMR) to suppress false positives
QDS for HL-LHC will be equipped with redundant interlocks and DQHDS triggers

7. QDS for HL-LHC: Polyvalent Analog Input Channel
Parameter
Value
Active input voltage range
±20 mV ... ±20 V
Max. differential input voltage
1 kV (1 sec)
Insulation withstand voltage level
5 kV (1 sec), 2.5 kV (10 min)
Resolution (20 Bit 1 Msps ADC)
40 nV/LSB μV/LSB
Cut-off frequency
100 kHz
J. Kopal

8. QDS for HL-LHC: Detection Algorithms
Appropriate set of voltage taps essential for QDS functionality
Classical bridge configuration for the suppression of periodic noise
Additional taps offering the possibility to detect safely aperture symmetric quenches
Dedicated sensor for current depending detection settings
Optional dI/dt sensor providing an alternative signal for QDS
Instrumentation scheme to protect a magnet assembly (= 11T Nb3Sn dipole)
against single- and multiple coil quenches.

9. QDS for HL-LHC: Signal Processing
Effective input signal filtering is crucial for the suppression of erroneous QDS triggers
New analog input stages have a relatively large bandwidth with a cut-off frequency of 100 kHz
Digital signal processing with tailor made filter chains adapted to the properties of the protected element
Non-linear filters for voltage spike suppression
FIR filters adapted to the LHC noise environment for high precision measurements, e.g. HTS leads, MgB2 links and superconducting bus-bars
QDS device configuration can be remotely updated and checked
Essential feature during system test and commissioning
Eases system maintenance significantly

10. QDS for HL-LHC: first real world tests
Partial flux jump measurements during test of MBHSP105 in SM18
Observation of violent but sharp voltage spikes, which can be easily filtered by median filter (red plot)!
Data recorded during 11.3 kA while ramping with 10 As-1

11. QDS for HL-LHC: System Dependability
QDS is a highly dependable system critical for LHC operation
2016 operation so far: 100% functional reliability (conditio sine qua non), 99.3% average overall system availability
This performance is compatible with HL-LHC operation
Maintainability can still be improved: less and shorter machine accesses, more options for automatic fault recovery and data analysis
System redundancy is the key element for attaining 100% reliability
Detection electronics, instrumentation voltage taps, powering by uninterruptable power supplies (UPS), controls interfaces, fast hardwired interlocks and active triggers for quench heater discharge power supplies and the novel coupling-loss induced quench protection systems (CLIQ)
Radiation tolerance
Most of the HL-LHC QDS will be installed in newly constructed radiation free underground areas in LHC points 1 and 5
Some QDS systems, e.g. for the 11 T dipoles will be exposed to moderate radiation levels of a few Gy/year (assuming 300 fb-1/year)

12. QDS for HL-LHC: Roadmap up to LHC LS2
Q R&D completed
Q Prototypes available
Q Type testing completed
Q Functional spec. QDS 11 T
SM18 tests!
PSI R2E tests!
CHARM R2E tests!
PSI R2E tests!
Q Eng. spec. QDS 11 T
Q Production QDS 11 T
Q Installation QDS 11 T
2020 Commissioning QDS 11 T
QPS IST I
QPS IST II

13. QDS for HL-LHC: Conclusion
The HL-LHC upgrade starting during LS2 of the LHC and to be completed in LS3 requires as well a major revision and upgrade of the LHC QDS
New development based on the substantial experience gained with LHC so far and taking into account recent advances in electronic components
First deployment of accelerator (LHC) grade quench detection systems for Nb3Sn magnets  important milestone
The R&D phase is expected to be concluded end 2016, first prototypes will be available in early 2017
All developments on track – no showstoppers identified so far
Operation of the first installed systems will start with the LHC hardware commissioning in 2020