Requested modifications to the 13 kA Energy Extraction Requested modifications to the 13 kA Energy Extraction Facilities and their ImplementationFacilities and their Implementation

Request for a faster current decay in the Main Dipole and Main Quadrupole CircuitsRequest for a faster current decay in the Main Dipole and Main Quadrupole Circuits The request is considered for operation at beam energies up to 4 TeV (The request is considered for operation at beam energies up to 4 TeV (~ ~ 6850 A), at least 6850 A), at least

for the momentfor the moment Consequences of switching with higher dump resistance from a given initial current (IConsequences of switching with higher dump resistance from a given initial current (I00):):

Larger decay rate ( dI/dt max = ILarger decay rate ( dI/dt max = Ioo / / ττ ) ) Higher voltages appearing across the extraction resistors and, consequently. applied to the Higher voltages appearing across the extraction resistors and, consequently. applied to the

magnet chainmagnet chain To be carefully checked: That the energy deposit in the DQRs in case of removal of parallel-To be carefully checked: That the energy deposit in the DQRs in case of removal of parallel-

connected resistor units does not exceed the tested limitsconnected resistor units does not exceed the tested limits Higher dump resistance can be obtained by either removing elements from a stack of Higher dump resistance can be obtained by either removing elements from a stack of

paralleled units or by adding series resistance. The first method will be used in the Dipole paralleled units or by adding series resistance. The first method will be used in the Dipole Chains, the second method in the Quadrupole Chains.Chains, the second method in the Quadrupole Chains.

Dipole Circuits: Rated values: 225 mDipole Circuits: Rated values: 225 mΩΩ / unit / 3 units in parallel, 2 systems / circuit, / unit / 3 units in parallel, 2 systems / circuit, ττ = = 102 s102 s

To stay below the commissioned values (except S56) we must not exceed:To stay below the commissioned values (except S56) we must not exceed:

dI/dt max = 91 dI/dt max = 91 A/sA/s

Umax = +/- 349 Umax = +/- 349 V to groundV to ground

E stored = 666 E stored = 666 MJ (59.5 % of MJ (59.5 % of nominal)nominal)

Requested modifications to the 13 Requested modifications to the 13 kA Energy Extraction Facilities and kA Energy Extraction Facilities and

their Implementationtheir Implementation

ττ Imax for remaining inside Imax for remaining inside commissioned valuescommissioned values

One unit disconnected, two One unit disconnected, two units in parallelunits in parallel

68 s68 s 6’200 A6’200 A

Two units series-connected, Two units series-connected, in parallel with the third in parallel with the third unitunit

51.3 s51.3 s 4’700 A4’700 A

Operation with only one Operation with only one unit per EE facility (two unit per EE facility (two units disconnected)units disconnected)

34.2 s34.2 s 3’100 A3’100 A

Main Quadrupole Circuits:

Consists equally of three, parallel-connected units

However, not disconnectable as welded structure.

Consequently, additional series-connected unit needed

Present values: 7.7 mΩ / 6.6 mΩ – giving τ = 30 s (incl. cable resistance)

Additional, CERN-made, plate resistor for external series-connection

1.80 mΩ / plate, 4 series-connected plates gives τ = 15 s ( 16.8 mΩ total incl. cable resistance)

Thus dI/dt max = 457 A/s , compared to 310 A/s as commissioned value.

Large margin to quench-back.

Max voltage to ground at 6850 A: 115 V – no problem

Requested modifications to the 13 kA Energy Extraction Requested modifications to the 13 kA Energy Extraction Facilities and their ImplementationFacilities and their Implementation

One complete Prototype Quadrupole additional resistor will be ready for testing this One complete Prototype Quadrupole additional resistor will be ready for testing this week. week.

Forced-air cooled, with dissipation in the UAs. Interlocked together with the present, Forced-air cooled, with dissipation in the UAs. Interlocked together with the present, water-cooled unit.water-cooled unit.

Mounted on the roof of the DQSB switch. Mounted on the roof of the DQSB switch.

If approved, all units can be produced and installed before 15 August.If approved, all units can be produced and installed before 15 August.

Requested modifications to the 13 kA Energy Extraction Requested modifications to the 13 kA Energy Extraction Facilities and their ImplementationFacilities and their Implementation

Additional Proposal for the Dipole Circuits: Additional Proposal for the Dipole Circuits:

Delay opening of one of the two switch assemblies of each dipole circuit in order to Delay opening of one of the two switch assemblies of each dipole circuit in order to attenuate the initial voltage transient attenuate the initial voltage transient

Note: Opening of both switches is already delayed (by 330 ms w.r.t. trigger signal i.e. Note: Opening of both switches is already delayed (by 330 ms w.r.t. trigger signal i.e. rupture of the quench loop) in order to assure that current decay occurs after beam rupture of the quench loop) in order to assure that current decay occurs after beam ejection (large margin)ejection (large margin)

Additional delay of 500 ms of odd-point switches suggested (RC = 510 kAdditional delay of 500 ms of odd-point switches suggested (RC = 510 kΩΩ x 3 x 3 μμF gives F gives 841 ms delay)841 ms delay)

Implementation on each of the eight OOC boards in the two BCM’s of one switch Implementation on each of the eight OOC boards in the two BCM’s of one switch assembly.assembly.