failures. A realis-
tic design might only incorporate some of the listed features.
Assumptions: The NLC will not be damaged by the sudden failure a a klystron 8-pack. Note that this may
not be true for up-stream sectors. The NLC can operate normally (after energy tuning) with a non-functional 8-pack. Minimal digital electronics in the tunnel. (This may change). Many cables must be available (for BPMS) for 300MHz bandwidth signals.
Redundant Systems:
Timing / RF:
Uses redundant timing design. Different 8-packs have independent connections to
the timing system. Tunnel RF measurements rely on local X-band beam pickoffs, and / or on
direct timing transmission on an independent cable.
Disadvantages: Increased system cost - requires 100 additional receiver and transmitter pairs.
Estimated NLC cost increase $3M - $6M.
Control system:
Dual networks are maintained within the sector to the 8-pack level. Within an 8-
pack a local network (if needed) is connected to both of the network. Local intelligence at the net-
work connection detects failure of one of the primary networks, and switches to the secondary.
The two sector networks use different technologies to reduce susceptibility to specic types of
interference.
All interlocks are local to an 8-pack, and will only trip that 8-pack. Machine interlocks
Disadvantages: Increased system cost - 2X number of TRIOs, Micros, and sector networks.
Guessed NLC cost increase $1M to $4M.
AC power distribution:
Only a design concept is shown. The actual system must be designed
with regard to normal good engineering practice. Power is fed to the sector building from each
end of a 480V local distribution bus. A 480V breaker is used to isolate high power faults in an 8-
pack modulator or other systems from tripping the main feed or other modulators.
The tunnel has dual 120V feeds, on from the upstream sector building, one from downstream.
Every critical device in the tunnel is fed with dual power supplies from each feed.
Disadvantages: Added cost due to dual sector transformers and switch gear. Added 120V wiring
in the tunnel. Water System:
There would be 9 independent water systems, one for each 8-pack. the water lines
from each system would be directed along the waveguide for the system, and used to cool the
structures driven by the 8-pac. Note that careful routing of these systems to Quads will provide
complete protection against single point water system faults.
Disadvantages: Greatly increased complexity due to 9 parallel water systems in the tunnel (each
with 1/9 of nominal ow).
Water system - variant: Two independent water system are constructed. All devices have dual
cooling channels, and can operate with one set of channels valved off.
Disadvantages: Increase cost and complexity of all high power devices.
Note: Neither of these water system redundancies seems practical.
MPS System
: The MPS system has the added complexity of requiring both fault tolerance and
fault intolerance. This is probably best achieved by using a 2/3 voting system. RF faults tend to be
isolated to a single 8-pack. If a sensor fails, and trips MPS, the entire 8-pack can be taken off line
and beam operation continued. Fault tolerance is not required below the 8-pack MPS interface
level.
RF fault detection will rely on matching sensor outputs to allowable waveforms. It is very improb-
ably that a sensor will fail so as to still generate an acceptable waveform when the actual RF is
bad. In addition, the MPS fault information can be encoded so that sensor processor failures are
unlikely to result in a false MPS OK signal.
Beamline / critical sensors are 3 way redundant, with voting in the MPS system. For some sensors
redundancy may be impossible, and high reliability must be designed into the sensor system.
Vacuum:
No Redundancy against leaks. Multiple pumps provide some redundancy.
Software:
Software is a common failure point and is very difcult to make fully redundant. For
example a bug in the RF drive code could send the wrong RF waveform to ALL klystrons in the
NLC - possibly causing severe damage. This remains an unsolved problem. 8-Pack #1
8-Pack #2
Note: only two 8-Packs shown for clarity
RF / Timing System
PHSCTR
RECEIVER
LLRF A-D/
D-A
Trig
X-Band
Mixers
RF ref
X8
X8
TWT
Diagnostic
RF Signals
Analog
and Logic
Signals
Modulator
Note: Triggers may be direct cables, or embedded
Digital
Control
Identical system
for each 8-Pack
Timing distribution A and B
Beam phase
phase and
Sbpm demod
Design assumes minimal digital hardware in the tunnel. 8-Pack #1
8-Pack #2
Note: only two 8-Packs shown for clarity
Control System
8-pack
LLRF
analog
system
Local digital
smarts
Dual network
Interface
TRIO A
TRIO B
To MCC
Modulator
Local network
Interlocks 8-Pack #1
8-Pack #2
Note: only two 8-Packs shown for clarity
Electrical Distribution
Xformer
low power
8-pack
LLRF
System
Modulator
Site Mains
~100Kv,
1500A
Site Mains
~100Kv,
1500A
Sector AC Mains
480V, ~2000A fed
both ends
Xformer/
switch
Xformer/
switch
480V breaker
Xformer
low power
120V
120V
Fed from next
sector
Sector Device
Dual power sup-
plies for all criti-
cal devices 8-Pack #1
8-Pack #2
Note: only two 8-Packs shown for clarity
Water System
Water pump
#1
Water pump
#1
Water pipes
connected to
RF distribu-
tion
waveguide
System uses 9 independent water pumps and distribution systems, one for each 8-pack.
This may be impractical to implement. 8-Pack #1
8-Pack #2
Note: only two 8-Packs shown for clarity
MPS System
LLRF
System
2/3 voting MPS channels
to main control
Local MPS net
Additional sensor for MPS / MAID /
FBA associated with 8-pack
Processor
Beam line / critical MPS sensors
- 3 way redundant 8-Pack #1
8-Pack #2
Note: only two 8-Packs shown for clarity