Linac4 BCC meeting

Scheme proposal for the Linac4 watchdogG Bellodi, B Mikulec, J-L Sanchez Alvarez

23/06/2011

Linac4 BCC meeting

Introduction

23/06/2011

Watchdog = Machine protection element whose function is to cut the beam if losses exceed predefined thresholds, depending on which user is being executed.

At Linac2 Software Interlock System (SIS) solution

1 FESA class providing the persistent configuration registry for some parameters (thresholds, counter, status, tolerance ranges for the BCTs

or the power supplies) +

2 hardware connections to the Interlock crate of LINAC 2.

The interlock crate disables (by HW) the timings for pulsing the source of LINAC 2 in case of raised interlock condition. A keep-alive pulse is generated by SIS at every cycle to ensure that the SIS and FESA are up and running (SW action that the FESA class turns into timing pulse to the interlock chassis) PPM counter linked to PSB timing

Linac4 BCC meeting 23/06/2011

Linac2 SIS flowchart

Linac4 BCC meeting

@ Linac4

23/06/2011

The Linac4 Watchdog acts via the Beam Interlock System – EDMS1016233Foreseen to be a maskable User Input of the BICs and can thus be disabled by the operators for particular operating scenarios

B Mikulec, B.Puccio

Linac4 BCC meeting 23/06/2011

L4 watchdog architectureFour parallel implementations (BIS design compatibility) are proposed:

1. Low-energy WD2. Linac4 and LT line WD3. LT-LTB-BI lines and LBE/LBS WD4. PSB injection WD

L4DUMP

LBE

PSB

LBS

a) Losses in the chopper cannot be covered (thresholds would have to depend on the chopping pattern used)

all BCTs upstream of LT.BHZ20 Linac4 frontend b) Readout:

all BCTs downstream of LT.BHZ20 BOR frontend

Linac4 BCC meeting 23/06/2011

1) Low energy Compares :

L4L.BCT.1183 & L4L.BCT.3113 for all beam destinations

Input to Master BIC ‘Source-RF’

2) Linac4 and LT line Compares :

a. L4L.BCT.4013 & L4Z.BCT.0117 (if dest=L4DUMP)

b. L4L.BCT.4013 & LT.BCT30 (if dest = LBE,LBS,PSB)

Input to BIC ‘Linac4 and Linac4 Transfer OK’

Linac4 BCC meeting 23/06/2011

3) LT/LTB and LBE/LBS/BI line watchdog Compares:

L4T.BCT.1617 & BI.BCT10 if dest=PSB L4T.BCT.1617 & LBE.BCT65 if dest=LBE L4T.BCT.1617 & LBS.BCT64 if dest=LBS (slit?)

Input to BIC ‘Linac4 and Linac4 Transfer OK’

4) PSB injection Compares:

BI(1:4).BCT20 & intermediate bandwidth transformer in section 8L1 (4, ring by ring)

Compares the sum of the 4 BI transformers with the sum of the 4 ring transformers (value taken after 100 turns) user per user .

Input to BIC ‘PSB OK(1)’

Linac4 BCC meeting

L4 WD Specifications/functionality

23/06/2011

Function: cut the beam if excessive losses are measured

1. on a user-by-user basis 2. after a certain number (set by the operators) of ‘bad’ pulses have been

recorded

FESA class receives information from the PSB telegram about which timing user (and destination) is being executed.

For each user, a Bad-Pulse-Counter is initialized to a maximum value and incremented/decremented if at every subsequent pulse according to whether this is good/bad.

When the Bad-Pulse-Counter=0 the watchdog triggers the interlock to cut the beam. A manual reset is needed (on a user-per-user basis) to restart operation.

On the basis of recent studies on beam induced damage scenarios (C Maglioni, BCC#25), the baseline assumed is that the watchdog should be able to react within 1 second (i.e. cutting the next pulse at 1Hz repetition rate after the detection of substantial losses in the machine) Rules out purely SW-based solution a` la Linac2.

Linac4 BCC meeting

Hybrid technology

23/06/2011

Hardware SoftwareBCTs equipped with TRICs (TRansformer

Integrator Card) for signal integration and ADC sampling

FESA-class super-structure for added functionality

registry of: user and destination thresholds information

BadPulseCounter update BCT readings comparison

Sensitivity 3 V = 100 mA

Maximimum intensity 100 mA

Accuracy, (Imin = 10 mA Imax= 100 mA) 1% rms

Precision, (fixed calibration) < 0.5% rms

Thermal sensitivity < 300 ppm / ⁰C

High frequency cutoff 7.8 MHz

Low frequency cutoff 0.7 Hz

Minimum pulse length (with an error < 1%) 100/200 ns

Maximum pulse length (with an error < 1%) 1 ms

Resolution (TRIC card) 5 mA

Maximum noise < 1 mA rms

Maximum noise for a gate of 1 ms (lower for narrower gate) < 5 E9

Linac4 BCC meeting

Watchdog flow-chart

23/06/2011

a. WD card provides an electrical interface to the CIBU modulesb. Hardware and software are in the same front-end (unlike Linac2)

 to reduce potential failure

Linac4 BCC meeting

Time action

23/06/2011

If counter ≠0 for the user to be executed,

the FESA class activates in the WD card a “watchdog

timing window” that enables beam

permit over ~2ms

Beam permit is disabled outside the WD timing

window

During the WD timing window, beam intensities are

acquired from the TRIC cards and

compared to WD thresholds-

BadPulseCounter is updated

BIC effectively re-armed at every pulse

Linac4 BCC meeting

Extra remarks

23/06/2011

A minimum intensity threshold should be implemented to avoid taking into account pulses with no beam (or triggering on noise). Current integration should be carried out as close as possible to the detector to avoid signal deterioration.

Redundancy needs to be built in the system and solutions sought to ensure fail-safe operation in case of failure scenarios and communication breakdowns .Duplicated inputs to the CIBU user interface per watchdog.

Keep-alive pulse coming from the SIS software should be generated at every cycle to ensure that FESA SW is up and running. If SW is not alive, no WD timing window is issued.

Operator needs to manually reset the watchdog (on a user-per-user basis) to restart operation.

WD architecture here presented matches currently proposed solution for the Linac4 BIS. Any changes to the latter will probably require modifications to the WD scheme shown...