LQS01 Test Preparation and

Test PlanLARP Collaboration Meeting 12

LBNL - April 8-10, 2009

G. Ambrosio, G. Chlachidze April 9, 2009

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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

G. Ambrosio, G. Chlachidze April 9, 2009

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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

G. Ambrosio, G. Chlachidze April 9, 2009

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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 ΔT 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 necessaryfor LQS01 to reach 4.5 K if temperature constraint is ΔT<150 K: Total of 4 days including overnight idling It will take ~4 times longer if ΔT< 50 K

LQSD Temperature at the top (black) andbottom (red) during helium cooldown

ΔT=50 K15 hrs

ΔT=150 K24 hrs

~ 30 hrsTo 200 K

T (K)

G. Ambrosio, G. Chlachidze April 9, 2009

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LQSD test experience (cont’d)

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 LQSD Temperature at the top (black) and bottom (red) during the N2 warm up

T (K)

G. Ambrosio, G. Chlachidze April 9, 2009

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LQS01 Test Preparation

Various improvements and upgrades are expected at the Fermilab’s 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.

G. Ambrosio, G. Chlachidze April 9, 2009

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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 voltagespikes 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.

Quench Detection System with Adaptive Thresholds

G. Ambrosio, G. Chlachidze April 9, 2009

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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 basedquench management system to VMTF has already been tested.

First full scale test will be done in 2nd half of April – at the end ofTQM02 test.

G. Ambrosio, G. Chlachidze April 9, 2009

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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 systemis designed for a max. of 1000 V)

Symmetric grounding was tested

several times and will be implemented on a permanent base in April.

2 5 O hm s

P SM agne t

Asym m e tr icG ro unding

Sym me tr icG ro unding

P SM agnet

1 00 O hm

1 00 O hm1 00 O hm

G. Ambrosio, G. Chlachidze April 9, 2009

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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 pointgrounded there would be no ground current as long as there are no faults to ground – we just raise theground 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.

Sym m e tr ic G ro undingwith Ac tive G ro und FaultD e te c t io n

P SM agne t

1 0 0 O hm

1 0 0 O hm

1 0 0 O hm

_+5 V

Thre s ho ldD e te c t io n

C irc ui t

Trg.

G. Ambrosio, G. Chlachidze April 9, 2009

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Active Ground Fault Monitoring System (cont’d)

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.

M agne t C o il + S tr ip H e ate rSym m e tr ic G ro undingwith Ac tive G ro und FaultD e te c t io n C irc ui tsP S

M agne t

1 0 0 O hm

1 0 0 O hm

1 0 0 O hm

_+5 V

Thre s ho ldD e te c t io n

C irc ui t

Trg.

Thre s ho ldD e te c t io n

C irc ui t

Trg.

_ +5 V

1 0 0 O hm

1 0 0 O hm1 0 0 O hm

G. Ambrosio, G. Chlachidze April 9, 2009

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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.

Magnet Protection System

G. Ambrosio, G. Chlachidze April 9, 2009

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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.

G. Ambrosio, G. Chlachidze April 9, 2009

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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

G. Ambrosio, G. Chlachidze April 9, 2009

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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.