LQS01 Test Preparation and Test Plan

1
LQS01 Test Preparation andTest Plan

• LARP Collaboration Meeting 12
• LBNL - April 8-10, 2009

2
Outline

• Introduction
• LQSD Test Experience
• LQS01 Test Preparation
• Quench Detection System with Adaptive Thresholds
• Symmetric Coil Grounding
• Active Ground Fault Monitoring System (Proposal)
• Reconfiguration of the Magnet Protection System
• Modified Strain Gauge Readout System
• LQS01 Test Plan (Draft)
• Summary

3
Introduction

• LQS01 test at Fermilab in Aug.-Sep. 2009 is an
  important milestone for the LARP magnet program
• LQS01 the first 4-m long Nb3Sn quadrupole to
  test in the Vertical Magnet Test Facility (VMTF)
  at Fermilab
• 4-m long Nb3Sn dipole coils previously were
  successfully tested
• More technological and mirror quadrupoles will be
  tested to investigate different magnet and cable
  parameters
• pre-load settings, new cable design, collar
  style
• Various elements of test facility need to be
  modified in order to meet LQ test program
  requirements

4
LQSD test experience

• LQSD Long quadrupole mechanical structure with
  dummy coils was successfully tested at Fermilab
  in 2nd half of March
• One of the important goals of the test was a
  cryogenic performance
• Trying to hold a certain temperature gradient ?T
  along the body of the magnet.
• Cool down performed using a helium
• gas flow. At 100 K, the vessel was filled
• with a liquid nitrogen.
• 48 hrs of cool down will be necessary
• for LQS01 to reach 4.5 K if temperature
• constraint is ?Tlt150 K
• Total of 4 days including overnight idling
• It will take 4 times longer if ?Tlt 50 K
• LQSD Temperature at the top (black) and
• bottom (red) during helium cooldown

T (K)
30 hrs To 200 K
?T50 K 15 hrs
?T150 K 24 hrs
5
LQSD test experience (contd)

• LQSD warm up took 6 days, 14 hrs were spent
  just to evaporate LN2. For
• LQS01 we will use a helium gas to warm up the
  magnet. We expect to reach 300 K in 4 days.
• Liquid helium volume in the vessel is 500 L
• LQSD test was very useful in
• preparation to LQS01 test
• To study mechanical performance
• To study cryogenic performance
• Obtained valuable experience of handling
• a 4-m long and 14000 lbs magnet

T (K)
LQSD Temperature at the top (black) and bottom
(red) during the N2 warm up
6
LQS01 Test Preparation

• Various improvements and upgrades are expected at
  the Fermilabs Vertical Magnet Test Facility
  (VMTF) in preparation to LQS01 test
• Some of these modifications were planned long
  time ago (symmetric coil grounding), while some
  improvements were initiated after LQSD test
  (modification of the SG readout system)
• All modified systems will be examined in advance
  when testing technological mirror quadrupoles
  (TQM)
• Detailed handling procedure was very helpful for
  LQSD test. We will prepare it for LQS01 test too
  along with the detailed run plan.

7
Quench Detection System with Adaptive Thresholds

• The Nb3Sn superconductor used in the 4-m long LQ
  magnets will produce relatively large voltage
  spikes. Raising the coil quench detection
  threshold adds delay to the quench detection time
  and the MIITs developed at high currents would
  exceed acceptable levels.
• Voltage spike analysis in various
• Nb3Sn magnets showed that both the
• magnitude and quantity of voltage
• spikes peak at a relatively low
• current, and then drop off as magnet
• current increases.
• This behavior will allow us to adjust the
• threshold dynamically to avoid trips at low
  currents while providing enough sensitivity at
  high current.

8
Quench Detection System with Adaptive Thresholds

• Proposed solution is to use the FPGA based quench
  management (QM) system already developed and used
  to test HINS solenoids at Fermilab.
• New FPGA based will work in parallel to the
  existing
• VxWorks based QM system.
• Interfacing an FPGA based
• quench management system
• to VMTF has already been
• tested.
• First full scale test will be done in
• 2nd half of April at the end of
• TQM02 test.

9
Symmetric Coil Grounding

• The 30kA DC power system used for testing magnets
  in VMTF is grounded at one point on the negative
  current bus via a 25 Ohm current limiting
  resistor.
• This "asymmetric" grounding configuration will be
  changed to a symmetric grounding scheme in
  which both the positive and negative bus will be
  grounded via two100 Ohm resistors to a center
  tap, which will be connected to ground through
  another 100 Ohm current limiting resistor.
• With symmetric grounding the
• maximum coil to ground voltage
• will be 500 V (the power system
• is designed for a max. of 1000 V)
• Symmetric grounding was tested
• several times and will be implemented on a
  permanent base in April.

10
Active Ground Fault Monitoring System (Proposal)

• An active ground fault monitoring system at VMTF
  was recently proposed in order to increase
  sensitivity to the detection of ground faults
  which would not depend on the location of the
  fault or the ramp rate and magnet inductance.
• An active ground fault detection circuit would
  include an isolated 5V voltage source in series
  with the ground resistor. Since this is the only
  point
• grounded there would be no ground
• current as long as there are no
• faults to ground we just raise the
• ground level of the symmetric
• grounding scheme to 5V above
• ground.
• In the event that a coil is shorted to ground
  then a voltage drop would develop across the 100
  Ohm ground resistor, which would trip the
  detection circuit when it reaches the desired
  threshold.

11
Active Ground Fault Monitoring System (contd)

• It is proposed that the strip heaters also be
  grounded using the symmetric grounding scheme and
  that the active ground fault detection be
  implemented as well.
• In this case system would not only detect a fault
  to ground but a fault
• between the coil and the strip heater.
• Currently internal review in progress
• to estimate required time and
• expenses. More discussions
• are expected.

12
Magnet Protection System

• Re-designed Magnet Protection System at VMTF
  includes 4 Heater Firing Units (HFU) for
  protection heaters and two HFUs for spot heaters.
• Heater distribution box was designed to
• accommodate up to 8 strip heaters in
• total.
• For LQS01 test we plan to connect 4 strip
• heaters in parallel internally and then
• connect to a separate HFU.
• All elements of the system are ready and
• will be tested by the end of April.

13
Modified Strain Gauge Readout System

• In order to boost the strain gauge signals in
  LQS01 magnet we plan to use 4 current sources.
• 2 Keithley current sources were used for 36
  strain gauges in LQSD magnet providing a maximum
  current of 1.25 mA.
• We plan to increase data saving rate by splitting
  the SG and RTD (temperature) scans
• Reference bridge was built at Fermilab for the
  calibration and monitoring of the strain gauge
  readout systems. Measurements with the LBNL
  portable and Fermilab SG readout systems showed
  very good agreement with the reference numbers.
• LQSD SG data were read out with the LBNL portable
  system before and after the test. During the test
  we used the Fermilab SG readout system. We will
  continue the same practice for LQS01 test.
• Modified SG readout system will be tested in
  June.

14
LQS01 Test Plan

• Primary test goal is to demonstrate performance
  with scale-up of coil length in Nb3Sn magnets.
  Among other objectives are study how a thermal
  cycle affects the quench behavior, quench
  training performance vs. temperature and ramp
  rate. Voltage Spike Detection system will be used
  to investigate instabilities and conductor motion
  during quench studies.
• 1st thermal cycle
• Quench training at 4.5 K followed with the cool
  down to 3 K.
• We will not test the magnet at a super-fluid
  temperature in 1st thermal cycle to avoid
  possible damage of coil.
• Temperature dependence study
• Warm up the magnet before 2nd thermal cycle
• RRR measurements
• 2nd thermal cycle
• Quench training at 4.5 K
• Quench training at 1.9 K
• Protection Heater Study

15
Summary

• Preparation to LQS01 test is in progress.
• Various elements of the vertical magnet test
  facility at Fermilab will be modified to meet LQ
  test program requirements
• FPGA based quench management system with adaptive
  thresholds
• Symmetric coil grounding
• Improved SG readout system
• Modified magnet protection system
• Active ground fault monitoring system (review in
  progress).
• All modified systems will be tested in advance -
  before the LQS01 test
• Mirror quadrupole (TQM) tests will be used for
  such a commissioning.
• Run plan with 2 thermal cycles is drafted for
  LQS01 test.