Overview of the CLIQ Units Project Knud Dahlerup-Petersen, Félix Rodríguez-Mateos TE-MPE Technical Meeting CERN, April 16 2015

Outline Introduction and general aspects Choice of main components Safety aspects The mini-Review and principal outcome A glance to the future of CLIQ The Team

Introduction and general aspects

A new hybrid protection system for high-field superconducting magnets Several units of CLIQ power supplies have been manufactured by the MSC Group over the last years and used at CERN for testing of different magnets in SM18 We do not present here the “ad-hoc” design of those units This previous design has given the needed flexibility to optimize parameters as capacity, voltage/current, frequency and dumping time constant There is now a request from MSC to the MPE Group to produce 3 units, 2 of which will be sent to FNAL by the end of May’15. The third one will serve as spare If successful, this project will continue with more prototypes and ultimately a production of series for Hi-Lumi upgrade magnets A new hybrid protection system for high-field superconducting magnets E Ravaioli, V I Datskov, G Kirby, H H J ten Kate, and A P Verweij

Some facts and boundary conditions The EE Section got the mandate in early February 2015 Delivery for end of May 2015 Choice of components was determined by the very short delivery time Resource organization was affected by the short lead time, with involvement of an important fraction of the section members Experience from the DQHDS is an important feature, although being of a different nature (only discharge)

Choice of main components

Capacitors (1) The CLIQ power unit is not only a supply, it is an energy exchanger This will lead to the characteristic ringing, which is being increasingly damped by the resistances in the circuit, mainly the rapidly increasing resistance of the quenching coil, but also by the series-equivalent resistance of the capacitor bank and cable leads The ringing leads to both positive and negative voltages on the storage capacitors within one current direction Typical CLIQ discharge (Emmanuele)

Capacitors (2): selection The storage capacitor bank for CLIQ must, according to above considerations, be of bipolar type Further requirements Low internal series-equivalent resistance High capacitance density Minimum bus bar work for connection Switch between 1 or 2 capacitors Selected type Self-healing, dry type, metallized polypropylene Data: 500 V, 2 x 40 mF, 2 x 44 kg (from LHC QF/QD snubber capacitor spares) With over-charge protection and over-pressure indication Stored energy: 10 kJ

Charging circuit The LHC 3-step type of charger is replaced by a 100 mA constant-current charger of commercial origin - tailored to our application. Full charging time around 400 s. Charging voltage shall be adjustable in steps of 50 V (manual commutation, up/down). Charging from 110 V, 60 Hz as from 240 V, 50 Hz. Capacitor voltage and charging current shall be displayed as well as the end of charging state. 16/04/2015 MPE Technical Meeting

Thyristors (1) Discharge characteristics of bi-directional nature (discharge / recharge currents) => semiconductor switches in a bi-directional arrangement have been chosen Good experience from the LHC quench discharge heater units with the use of thyristor switches => decision to keep the thyristors option for the CLIQ units Thyristors will be used in both directions in order to assure a ‘certain separation’ of the main magnet powering circuit from the heater circuit outside the provoked coupling period The two opposite thyristors shall be fired simultaneously for 0.5 s. No trigger redundancy in each unit is considered necessary

Thyristors (2): selection Two candidate thyristors have been considered: Single Thyristor used for fast opening pulse to LHC main circuit energy extraction switches (BCM). To be doubled Bi-directional Thyristor for energy management. Approved by ABB for the CLIQ application. Two thyristors in one wafer The thyristor firing shall be provoked through application of a train of pulses, from a 12 kHz generator through pulse transformers. Discharge current shall be measured by adequate AC current transformer (6kA peak, 10-3 accuracy). 1. 2.

Safety aspects

A main breaker (or a switch + fuse), accessible on the outside panels of the CLIQ unit, shall assure not only interruption of the input power but equally switch-in a bank of discharge resistors which will assure an automatic ‘internal’ discharge of the complete capacitor bank. The total discharge time shall be 1 minute maximum. In addition to a clear indication of the actual charging voltage/current (analog voltmeter or galvanometer per capacitor), a visible indicator shall show safe conditions (<40V). After re-powering from the mains input, there shall be no automatic re-charging of the capacitor bank (system is latched). Charging shall be initiated manually. After a discharge the system is automatically latched. Recharging only by manual activation. Activation of the equipment stop button shall initiate an internal discharge of the capacitors For changing the capacitance value (switch between 1 or 2 capacitors), possibilities should be studied that do not imply opening of the rack (lockable switch that can only be activated after discharge of the capacitors)

The mini-Review and principal outcome

Objectives Validation of the implementation of the concept Coherence of the choices with respect to the established functionalities Correctness with integration and implementation according to the electrical standards applicable Safety aspects

Panel Jean-Paul Burnet, TE/EPC Alexandr Erokhin, TE/MPE José Carlos Gascón, DGS-SEE-XP Christian Giloux, TE/MSC Andrzej Siemko, TE/MPE (ex-officio) Yves Thurel, TE/EPC The mini-Review took place on April 8, 2015

Agenda 1. Scope and objectives of the review Félix Rodríguez Mateos 10’ 2. Introduction to the CLIQ protection method Emmanuele Ravaioli 15’ 3. General aspects of the design, choice of components and safety issues Knud Dahlerup-Petersen 4. Details of the design Joaquim Mourao 30’ 5. Integration and implementation Mathieu Favre 6. Discussion and questions from the panel All

Recommendations (1) Components use the higher rated ABB thyristors which give larger margin in all parameters set 0.5s for the duration of the train of pulses discharge resistors should not to be mounted on a PCB, 20 resistors in series should not be used thyristor firing circuit to be completed (paying attention to magnetization of the pulse transformers) use an AC current transformer instead of a LEM for discharge current measurement qualify the AC/DC converter in terms of EMC or use qualified material 16/04/2015 MPE Technical Meeting

Recommendations (2) Safety Project Management maximum discharge time should be 1 min use a switch that a) triggers internal discharge, b) short-circuits capacitors and c) allows opening the cubicles (if required) use a properly rated circuit breaker for ON/OFF and not a “sectionneur”, or add a fuse earthing issue: for such mobile units as the ones under discussion the earth connection given through the powering mains is enough no need for special screws, idem for internal plastic covers install galvanometers to show the charge/discharge of each capacitor Project Management prepare test programme well in advance prepare documentation for the future users structure the project (mandate, functional specifications, technical specifications, planning, responsibilities, etc) 16/04/2015 MPE Technical Meeting

A glance to the future of CLIQ

Near future plan for protecting magnets with CLIQ LHC-high luminosity upgrade QXF is the inner triplet large quadrupole strings of magnets either side of the ATLAS and CMS. Model testing in Fermi-lab (two units plus spare) Model testing in CERN (Two units plus spare) First long magnet prototype test in BNL (Two units plus spare) Production of 32 + spares units for LHC-HL, assuming two units per magnet. Courtesy Glyn Kirby

Longer term possibilities for use in LHC-HL upgrade CERN Orbit correctors for LHC-HL: Twin aperture independently powered dipole MQY for LHC-HL with pushed performance for the upgrade. Currently being tested in SM 18 at CERN. Each magnet would need 4 units LHC: Main dipole will be tested at CERN in SM18 in the following months in view for rapid repair of LHC systems Outside CERN KEK Japan: D1, LHC-HL Single aperture standalone dipoles requiring 4 units + spares CEA France: Q4 Twin aperture quadrupoles ~ 16 units + spares GSI: they are investigating for use with their magnet systems Further future 16 Tesla hybrid FCC models block design & cos-theta design could benefit from CLIQ CCT design (canted cosine theta) may rely on CLIQ; LBNL have requested two units for future testing of their 16 Tesla CCT magnet.

The team

Members of the team in MPE Knud Dahlerup-Petersen Arnie Dinius Mathieu Favre Joaquim Mourao Bozhidar Panev Emmanuele Ravaioli Felix Rodriguez Mateos Other contributors: Gert Jan Coelingh Alexandr Erokhin Yan Bastian