Design and Fabrication of the 1.9 K Magnet Test Facility at BNL, and Test of the First 4m Long MQXF Coil J. Muratore, M. Anerella, P. Joshi, P. Kovach, A. Marone, P. Wanderer

The future high luminosity upgrade of the Large Hadron Collider (LHC) at CERN will include twenty 4.2 m long Nb3Sn high gradient quadrupole magnets which will be components of the triplets for two LHC insertion regions. In order to test these and four pre-production models, the vertical superconducting magnet test facility of the Superconducting Magnet Division (SMD) at Brookhaven National Laboratory (BNL) has been upgraded to perform testing in superfluid He at 1.9 K and 1 bar, which is the operational condition at the LHC. This has involved extensive modifications of the 40-year old, 4.5 K cryogenics plant at SMD. These upgrades include new piping, compressors, and other critical components, a new vertical test cryostat with top plate and hanging fixture which can accept larger diameter and longer magnets, up to actual length 5 m long, a 1.9 K heat exchanger, newly designed warm bore tube, and a lambda plate designed with a novel seal configuration for both strength and minimum heat loss. In addition, the former short sample cable test facility 30 kA power supply has been upgraded with an energy extraction system using IGBT switches and fast shutoff capability, and a new high energy dump resistor, and reconfigured to supply 24 kA to test high field Nb3Sn magnets.

We have also assembled completely new data acquisition, signal analysis, and control software and hardware, allowing for high precision and large volume data collection. This paper describes the design, assembly, and commissioning of the upgraded test facility and the first magnet test performed, on a mirror model, which consists of a single coil quadrant and an iron yoke filling the other three quadrants and is designed to have peak fields close to that of the production quadrupoles. The mirror coil was the first long coil of the MQXF design to be tested.

Mon-Af-Po1

MQXFA TEST PARAMETERS

Vertical Test

Dewars 2-6

HORIZONTAL TEST STAND A

HORIZONTAL TEST STAND B

HORIZONTAL TEST STAND C

HORIZONTAL TEST STAND D

HORIZONTAL TEST STAND E

CONTROL ROOM

MQXF

30 kA Power

Supply

2.7 m Deep Test Dewars 6.1 m Magnet Deep Test Dewars

CTI 4000 He

Refrigerator

CVI Air Liquide

He Refrigerator

Nash “high

capacity” vacuum

Pump (1.9K)

SMD TEST FACILITY FLOOR PLAN Mycom 800 hp

Compressor

(2 Stages)

160 g/s

Sullair 500 hp

Compressor

(Single Stage)

80 g/s

Sullair 350 hp

Compressor

(Single Stage)

51 g/s

Buffer

Tank

Reciprocating

Helium Expander

CTI Model 4000

1500 W

Refrigerator/

Liquifier

CVI – Magcool

Precooler/Subcooler

(Cold Box)

Turbo-Expander

Helium

Liquifier

CVI/Air Liquide

1000 W

Helium Wet Expander

Koch Model 1600

Cryenco

Inline Purifier

Cryenco

10000 Liter

Storage Dewar

High Pressure

Helium Gas

High Pressure

Helium Gas

@ 8K

Liquid

Helium

Liquid

Helium

Warm Return

1.8 K Test Dewar 2

Cryenco

3785 Liter

Storage

Dewar

Gardner

3785 Liter

Storage

Dewar

Dual

Turbines

High Pressure

Helium Gas

Lambda

plate

Warm Return

Buffer Tank

to Suction CS4

Sullair 100 hp

CS4

1.8 K Test Cryostat

2-Stage CVI/Magcool Purifier A & B

Liquid Helium

Storage Dewar

10000 L

High Pressure Helium

Gas Storage

8.5 x 106 L @ 15.5 bar

Nash 1.8 K Vacuum

Station

As proposed: Using existing infrastructure for the new 1.8 K Testing Facility

Buffer Tank

to Helium Gas

Storage

Warm Helium Return

4.5 K Helium Input

1.8 K

4.5 K

16 mbar1 bar

SMD MAIN CRYOGENICS FACILITY 1.9 K PROCESS FLOW DIAGRAM

Magnet &

Cryostat

24 KA Cable (60 ft)

CLIQ Circuit

CERN Built

REE1,

Energy

Extraction

Resistor

REE2,

Energy

Extraction

Resistor

S2, 6 IGBT

Switches In

Parallel

S1, 6 IGBT

Switches In

Parallel

DCCT

DCCT

30 VDC

15KA

Power

Supply

30 VDC

15KA

Power

Supply

BNL Built Control For

CLIQ Circuit

High Voltage Power

Supply Control

BNL Built Quench

Detector

IGBT Control Power Supply Control

Filter

Filter

Main PS

Tc

Main PS

Vo

CLIQ Switch

Control

C

P. Joshi. BNL July 18 2017

Current

Sensor

D2

24 KA Cable (60 ft)

D2

D3

D3

1000 Amp Shunt

15 KA Cable (85 ft)

L1

L2

L3

L4

20 DIODES

15 kA / 14 V

Power Supply

6 Pulse SCR

Bridge3 Phase

480 V

X 6

15 kA DCCT100 µH

15.5 mF

85 mΩ

62.0 mF

15 kA water-cooled cable

24 kA water cooled cable

15 kA water-cooled cable

15 kA / 14 V

Power Supply

6 Pulse SCR

Bridge3 Phase

480 V

X 6

15 kA DCCT100 µH

16.0 mF

85 mΩ

81.9 mF

33 mΩ

15 kA water-cooled cable

33 mΩ

15 kA water-cooled cable

IGBT (6 parallel units) Switch

with snubber circuits

IGBT (6 parallel units) Switch

with snubber circuits

24 kA water cooled cable

24 kA Vapor-Cooled Leads

1.9 K

4.5 K

800 mF

800 mF

1 Ω

33 mΩ 33 mΩ

1 Ω

30 kA POWER SUPPLY SYSTEM WITH ENERGY EXTRACTION 30 kA POWER SUPPLY SYSTEM WITH CLIQ

QUENCH DETECTION The MQXFA quench detection system is based on a redundant scheme which relies on a number of voltage signals. When any one of the following signals reaches its specified threshold voltage after a specified validation time, a fast discharge is instigated (current decays through dump resistor). Typical threshold voltages and validation times are listed here.

1) Half coil voltage Vhalf1 - Vhalf2 50-250 mV 2-5 ms

2) Quarter coil voltage V1 – V2 50-250 mV 2-5 ms

3) Quarter coil voltage V3 – V4 50-250 mV 2-5 ms

4) Total coil voltage Vtotal 50-250 mV 2-5 ms

5) SC lead voltages VSCL+ and VSCL- 10-50 mV 2-5 ms

6) Splice voltages V12, V34, V24 8-10 mV 2-5 ms

7) Current Derivative Vtotal – L dI/dt 0.1-1.0 V 5-10 ms

Note: The above thresholds are for currents higher than 6 kA. In Nb3Sn magnets, current-dependent thresholds as high as several volts at low currents are necessary and are set in the software. This is to avoid false QD trips due to flux jump spikes.

There are also designed into the system a number of interlocks which also rely on various signals which, if they do not meet specified conditions such as voltage threshold or on-off state, will instigate a slow discharge, with the dump resistor out of the circuit. These include:

1) Vapor-cooled lead voltages 80-100 mV 500-1000 ms

2) Strip heater capacitor bank not charged

3) IGBT switch temperature or voltage too high

4) Others

• (2) 24 kA main coil vapor-cooled leads

• (2) 1 kA CLIQ vapor-cooled leads

• (3) instrumentation wiring trees

• (2) helium fill lines

• Heat exchanger port, 3rd CLIQ lead port

• Manifolds and solenoid valves under plate

• Warm bore tube port

• Helium vent port

1.9 K MQXFA TOP PLATE DETAILS

New Top Plate

Lambda Plate

Redesigned Inner

He Vessel

Existing Outer

Dewar

MQXF Magnet

4.5 K Heat Shield

Top is 38.1 mm thick G10 (lower heat

load)

Bottom is 19.05 mm thick 304

stainless steel (for added strength

and sealing to He vessel interior

flange)

Bonded together with Stycast

2850FT

Total heat load < 1.4 W

New top plate to accommodate

lambda plate and fixturing for

MQXF 4.2 m quads and 24 kA

vapor-cooled leads and heat

exchanger for 1.9 K, 1 bar

operation.

Rated at 5.86 bar

Components below lambda plate

and internal to heat exchanger are

designed for 5.86 bar,

above lambda plate for 3.45 bar.

NEW RE-DESIGNED TEST CRYOSTAT FOR 1.9 K AND 24 kA

Heat

exchanger

CLIQ LeadsConnector Trees

Quench Heater Connector Tree

24 kA vapor-cooled leads

Top plate 76.2 mm

thick 304 SS

He fill lines

3rd CLIQ Lead

(if needed)

NEW 1.9 K LAMBDA PLATE DESIGN

FAST DATA LOGGER DAQ National Instruments PXIe-4300 (16 Units)

Number of channels = 8 differential, simultaneous sampling

Analog input = ±10 V, ±5 V, ±2 V, ±1 V

ADC resolution = 16 bit

Sampling rate = 250 kHz max per channel

Time scale resolution = 10 ns

TOTAL CHANNELS = 128 differential, simultaneous sampling

Usage = fixed (main) voltage taps and configurable (auxiliary)

voltage taps

Status: Assembled and Tested

SLOW DATA LOGGER DAQ National Instruments PXI-6289 (4 Units)

Number of channels = 16 differential

Analog input = ±10 V, ±5 V, ±2 V, ±1 V, ±0.5 V, ±0.2 V, ±0.1 V

ADC resolution = 18 bit

Sampling rate = 500 kHz max multichannel (31.25 kHz max)

Time scale resolution = 50 ns

TOTAL CHANNELS = 64 differential

Usage = monitoring of vapor-cooled lead voltages, splice

voltages, SC lead voltages, temperatures, LHe levels, and

other instrumentation

Status: Assembled and Tested

64 Channel

Slow Logger

128 Channel Fast Logger

FASTER HIGHER PRECISION DATA ACQUISITION SYSTEMS

TEST FACILITY COMMISSIONING MQXFPM1 MIRROR MAGNET

FIRST LONG MQXF COIL

10000

11000

12000

13000

14000

15000

16000

17000

18000

19000

20000

21000

22000

23000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

QU

ENC

H C

UR

REN

T (A

)

QUENCH NUMBER

MQXFPM1 TRAINING QUENCHES

A3-A4 Pole Multiturn (at 3.25-4.3K)

A5-A6 Pole Turn Long Straight Section

A6-A7 Pole Turn NonLead End Section

A7-A8 Pole Turn Short Straight Section

A8-B8 Ramp

B3-B2 MIDPLANE MULTITURN

THERMAL CYCLES

NO QUENCH - 50A/s to 10kA then 20A/s

NO QUENCH - 50A/s

NO QUENCH- 20 A/s

Quenches 1-12 and 14-17 were at 20A/s.Quench 3 was in A6-A7 but close to or at tap A7.Quench 13 was at 20A/s with 2hr hold at 17890A.

NO QUENCH

4.424K

NO QUENCH

SS 22095A

ULT 17890A

NOM 16480A

300 A/s 3.265 - 4.424K

144K (TOP) - 110K (BOT)

117K (TOP) - 77K (BOT)

Lambda plate sealing detail

Lo

wer

He

ves

sel

Oute

r 4

K h

eat

shie

ld

He

ves

sel

flan

ge

G-10/SST Lambda plate

Lambda Plate Spring-Energized Face Seal to He Vessel

Eight 600 V 12.4 mF Units

Four 900 V 13.05 mF Units

QUENCH PROTECTION HEATER FIRING UNITS FOR 12 INDEPENDENT CIRCUITS

CLIQ (Coupling Loss-Induced Quench) is a system which provides quench protection, along with quench heaters and energy extraction.

CONCLUSION As can be seen by the quench training results for the MQXFPM1 magnet, the upgraded facility as described here successfully fulfilled the acceptance test requirements for the MQXFA quadrupole magnets which are being built and supplied to the LHC for the insertion region Q1/Q3 of the high luminosity upgrade. These requirements include operation at 1.9 K at 1 bar, powering up to 19 kA, and proper protection of the magnet during quench testing. For the test of the MQXFPM1, quench protection included a newly designed and faster quench detection system, energy extraction with faster and state-of the-art electronic switching using specially designed IGBT circuitry and infrastructure. Future magnets will be using the already upgraded energy extraction system with a higher power and more versatile dump resistors, and twelve new quench protection heater firing units, which meet the requirements for quench protection heater systems in the LHC.

Coil inner aperture D = 150 mm

Coil magnetic length l = 4.2 m

Coil actual length l = 4.523 m

Yoke length l = 4.5629 m

Total length with end plates l = 5 m (nom)

Operational temperature T = 1.9 K

LHC nominal operating current (1.9 K) Inom = 16.470 kA

LHC ultimate operating current (1.9 K) Iult = 17.890 kA

Maximum current (300 K) I300 = 10 A

Conductor limit at 1.9 K Iss = 21.600 kA

Conductor limit at 4.5 K Iss = 19.550 kA

Peak field in the coil at Inom (1.9 K) Bnom = 11.4 T

Peak field in the coil at Iult (1.9 K) Bult = 12.3 T

Peak field in the coil at Iss (1.9 K) Bss = 14.5 T

Field Gradient at Inom (1.9 K) Gnom = 132.6 T/m

Field Gradient at Iult (1.9 K) Gult = 143.2 T/m

Field Gradient at Iss (1.9 K) Gss = 168.1 T/m

Magnet resistance at room temperature R = 2.37 Ω

Magnet inductance (20Hz at room temperature) LRT = 38.1 mH

Magnet inductance (at 1.9 and 1 kA) L1 = 40.9 mH

Magnet inductance (at 1.9 and Inom=16.5 kA) L16.5 = 32.8 mH

Operating stored energy (at Bnom, Inom) Emax = 4.5 MJ assuming L=32.8 mH

Maximum allowed temperature at quench Tmax = 350 K

Maximum allowed voltage across magnet Vmax = 1000 V (500 V to ground) with 50 mΩ EE

Dump resistor (energy extraction) options RD = 30, 37.5, 50, 75, 150 mΩ

Overall test fixture and hanging assembly (insert), shown with mirror magnet MQXFPM1.

Diagram courtesy of W. McKeon, Cryogenics Facility Diagram courtesy of W. McKeon, Cryogenics Facility