AT-MEI-PE, RD, LIUWG 31-JUL-2008 1 R. Denz AT-MEI-PE LHC Luminosity Upgrade Protection of the Inner Triplet, D1, Correctors and Superconducting Links/Leads.

AT

-ME

I-P

E,

RD

, LI

UW

G 3

1-JU

L-20

08

1

R. Denz AT-MEI-PE

LHC Luminosity UpgradeProtection of the Inner Triplet, D1, Correctors and

Superconducting Links/Leads

AT

-ME

I-P

E,

RD

, LI

UW

G 3

1-JU

L-20

08

2

Outline

Protection of IT corrector circuits

D1 protection

Inner triplet protection

Conclusions

AT

-ME

I-P

E,

RD

, LI

UW

G 3

1-JU

L-20

08

3

Protection IT corrector circuits today

Standard protection system for LHC corrector magnet circuits with dedicated QPS

– Midpoint voltage tap not available

– Requires additional current sensor and sophisticated digital detection electronics

– Dedicated protection system for HTS leads

AT

-ME

I-P

E,

RD

, LI

UW

G 3

1-JU

L-20

08

4

Protection IT corrector circuits after upgrade

Bridge based protection system using asymmetric midpoint tap

– Radiation tolerant version feasible using analog circuitry

– Enhanced noise immunity

Energy extraction system can be based on mechanical circuit breakers or on semiconductor devices

Dedicated protection system for HTS leads and/or links

– Voltage taps, thresholds etc. still to be defined

Space requirements for complete system:

– 0.5 x 19’’ rack per circuit

AT

-ME

I-P

E,

RD

, LI

UW

G 3

1-JU

L-20

08

5

Protection IT corrector circuits after upgrade

Bridge based protection system

– Already in use for D1 in point 2 and 8

Dedicated protection system for HTS leads and/or links

Space requirements for complete system:

– 0.5 x 19’’ rack per circuit

AT

-ME

I-P

E,

RD

, LI

UW

G 3

1-JU

L-20

08

6

IT protection today

Advantages

– It works !

– Limited space requirements (2 standard 19’’ racks only)

Drawbacks

– Relies on functionality of cold quench heater circuits

– Dumps stored energy into He bath

AT

-ME

I-P

E,

RD

, LI

UW

G 3

1-JU

L-20

08

7

IT protection after luminosity upgrade I

Different options for protection of the magnets and superconducting bus-bars

– Quench detection always based on bridge configuration

Dedicated protection system for HTS leads and/or links

Protection schemes can be easily adapted to other triplet layouts

Choice depends strongly on boundary conditions

– Radiation levels

– Available space

courtesy D. Nisbet, R. Ostojic

AT

-ME

I-P

E,

RD

, LI

UW

G 3

1-JU

L-20

08

8

IT protection after luminosity upgrade – options I

Quench heaters only

– Equivalent to insertion region magnet protection in LHC

• Works as well with one detector for both magnets

– Heaters of both magnets always fired energy dumped in He bath

– Robust, radiation tolerant, small (1 x 19’’ rack for two magnets)

– System can be build with existing designs – some components may be re-used

– As an option the development of a new quench power supply allowing long distance feeding and different heater pulse shaping is feasible

AT

-ME

I-P

E,

RD

, LI

UW

G 3

1-JU

L-20

08

9

IT protection after luminosity upgrade – options II

Quench heaters, warm by-pass and energy extraction

– Only heaters of quenching magnets are fired, warm by-pass (thyristor) and energy extraction system activated

• Other magnets will only quench due to propagation

– Cold by-pass (like for MB, MQ) is excluded due to high radiation load

– Semiconductor based energy extraction systems

• IGCT (Integrated Gate Commutated Thyristor) in parallel with a DC contactor

• DC contactor carries the current in closed state; IGCT ruptures the current in case of trigger

• Possible in radiation free area only – about 4 x 19’’ racks for two magnets (complete system)

– Mechanical circuit breakers

• Can be used in present areas as those systems are radiation tolerant

• Main constraints are space, procurement and maintenance

AT

-ME

I-P

E,

RD

, LI

UW

G 3

1-JU

L-20

08

10

IT protection after luminosity upgrade – options III

Quench heaters and energy extraction

– dI/dt created by energy extraction system will exceed quench-back limit

– Both magnets will be quenched but most of the energy will be transferred to dump resistor

• Less stress for magnet and cryogenics

• Faster cooling after quench possible

– Quench heaters will be fired as well but serve basically as a back-up

– Warm by-pass is not required

– Space requirements: about 4 x 19’’ racks for two magnets

• Valid for semiconductor based energy extraction system

AT

-ME

I-P

E,

RD

, LI

UW

G 3

1-JU

L-20

08

11

Conclusions

Protection of inner triplet correctors and D1 based on established designs and technologies

– In case correctors are powered with I > 600 A protection can be adapted

Protection of inner triplet

– Compatible with all powering layouts currently in discussion but the split powering solution is the preferred option

– Several options for protection possible – final choice will depend on boundary conditions

– Location of protection systems to be defined prior to any further development

– There won’t be sufficient manpower for extensive new developments

• Re-use of existing designs with necessary modifications applied

• Use of components available in industry (e.g. for energy extraction systems)