The Constant Fraction Discriminators CFD8c, CFD7x, CFD4c, CFD1c and CFD1x (11.0.1701.1)
Page 24 of 25
List of Figures
F
IGURE
3.1
B
:
T
HE
CFD8
(
HERE
:
CFD8
B VERSION
),
CFD7
X SIMILAR
.................................................................................... 6
F
IGURE
3.2
B
:
P
HOTOS OF THE
CFD4
AND
CFD1
SERIES CASES
(
HERE
:
‘
B
’
VERSIONS
)
AND THE
SPS3
POWER SUPPLY
.......... 7
F
IGURE
3.3
B
:
F
RONT PANEL INPUTS
,
TEST POINTS AND CONTROL POTENTIOMETERS
,
NOT SHOWN IS THE VETO INPUT AND
THE
CFD
FRACTION
POTENTIOMETER BEING ON THE FRONT PANEL FOR C AND X VERSIONS
(
SEE
F
IGURE
3.14) ............. 8
F
IGURE
3.4
B
:
S
CHEMATICS OF A
CFD
ANALOGUE CHAIN
...................................................................................................... 8
F
IGURE
3.5
B
:
TOP
/
SIDE PANEL WITH FRACTION POTENTIOMETER ONLY VERSIONS A
/
B
)
AND OPTIONAL JUMPER TERMINAL
FOR INCREASING THE
CFD
OUTPUT WIDTH BY A FACTOR OF
10
(
OPTIONAL
) ................................................................. 9
F
IGURE
3.6
B
:
S
CHEMATICS OF THE
CFD
DIGITAL CIRCUIT CHAIN
......................................................................................... 9
F
IGURE
3.7
B
:
O
SCILLOSCOPE TRACES OF IN
-
AND OUTPUT SIGNALS OF THE
CFD,
TRACES
1-4
FROM TOP
:
INPUT SIGNAL
,
ANALOGUE MONITOR OUTPUT SIGNAL
,
DIGITAL MONITOR OUTPUT SIGNAL
,
CFD
TIMING OUTPUT SIGNAL
(
WHICH
TRIGGERS ALL TRACES
).
T
HE RED ARROWS INDICATE THE
TIMING TRANSITION
WHICH APPEARS SLIGHTLY SHIFTED IN
THE DIFFERENT TRACES DUE TO INTERNAL DELAYS
.
T
HIS AND THE FOLLOWING IMAGES OF SIGNAL TRACES HAVE BEEN
OBTAINED WITH A
300 MH
Z ANALOGUE OSCILLOSCOPE
(
A LARGE NUMBER OF SIGNALS WITH VARYING PULSE
HEIGHTS ARE SUPERIMPOSED
).
S
IMILAR VIEWS CAN BE OBTAINED FROM DIGITAL OSCILLOSCOPES WITH ADEQUATE
“
PERSISTENCE
”
SETTING
.............................................................................................................................................. 10
F
IGURE
3.8
B
:
S
IGNAL TRACES SIMILAR AS IN
F
IGURE
3.7
B FOR POORLY ADJUSTED
T
HRESHOLD LEVEL
:
ANALOGUE MONITOR
OUTPUT
,
DIGITAL MONITOR OUTPUT
(
ONLY IN LEFT PICTURE
)
AND
CFD
OUTPUT
.
L
EFT PICTURE
:
FOR TOO HIGH
THRESHOLD SETTINGS ONLY INPUT SIGNALS WITH VERY HIGH AMPLITUDES ARE REGISTERED
.
W
HEN SETTING THE
CORRECT
T
HRESHOLD LEVEL
,
THE DARK AREA SHOWN BY THE ARROW WOULD BE FILLED WITH SMALLER AMPLITUDE
SIGNALS
.
R
IGHT PICTURE
:
THRESHOLD SETTING TOO LOW
(
I
.
E
.
IN THE NOISE
) ............................................................. 11
F
IGURE
3.9
B
:
S
IGNAL TRACES
(
AS IN
F
IGURE
3.8
B LEFT
)
BUT WITH TOO LONG
(
LEFT PICTURE
)
AND TOO SHORT DELAY
CABLE
(
RIGHT
) ............................................................................................................................................................. 12
F
IGURE
3.10
B
:
S
IGNAL TRACES
(
AS IN
F
IGURE
3.8
B LEFT
)
WITH A TOO SHORT DELAY CABLE
(
LEFT PICTURE
).
T
HIS CAN
FAIRLY BE COMPENSATED BY INCREASING THE
CFD
FRACTION FROM
0.35
TO
0.6
(
RIGHT PICTURE
) ........................... 12
F
IGURE
3.11
B
:
S
IGNAL TRACES
(
AS IN
F
IGURE
3.8
B LEFT
)
WITH DIFFERENT
CFD
FRACTIONS
:
LEFT PICTURE F
=
0.35,
RIGHT
:
F
=
0.7 .......................................................................................................................................................................... 13
F
IGURE
3.12
B
:
S
IGNAL TRACES
(
AS IN
F
IGURE
3.8
B LEFT
)
WITH THE WALK LEVEL SET TO THE BASELINE OF THE INPUT
SIGNALS
(
LEFT PICTURE
)
AND SLIGHTLY TOWARDS THE POSITIVE SIDE WHERE THE NOISE TRIGGERS BEGIN TO VANISH
(
RIGHT PICTURE
),
LEADING TO SLIGHTLY LESS INTENSITY IN THE AREA RIGHT OF THE ARROW
.................................... 13
F
IGURE
3.13
B
:
S
IGNAL TRACES
(
AS IN
F
IGURE
3.8
B LEFT
)
WITH THE
W
ALK LEVEL SET TOO LOW
(
LEFT PICTURE
)
AND TOO
HIGH
(
RIGHT PICTURE
) ................................................................................................................................................. 14
F
IGURE
3.14
B
:
P
OSITION OF
V
ETO INPUT SOCKET ON THE
CFD8
C FRONT PANEL
.
F
OR THE
CFD4
C IT IS FOUND ON THE REAR
PANEL
.......................................................................................................................................................................... 15
F
IGURE
3.15
B
:
T
RACE OF THE INPUT SIGNAL TO THE
V
ETO SOCKET
(
UPPER TRACE
)
AND SIGNAL TRACES OF
CFD
TIMING
SIGNALS
(
LOWER TRACE
,
INTEGRATED OVER MANY EVENTS
)
FOR
V
ETO
(
LEFT
)
AND
G
ATING MODE
(
RIGHT
) .............. 15
F
IGURE
3.16
B
:
J
UMPER
B
LOCK
(
HERE
:
INSIDE
CFD1
C
)
FOR DEFINING THE LOGIC MODES
:
V
ETO
(
LEFT PICTURE
,
DEFAULT
SETTING
),
G
ATING
(
MIDDLE PICTURE
)
AND
N
EUTRAL
(
RIGHT PICTURE
) ...................................................................... 15
F
IGURE
3.17
B
:
F
RONT AND REAR PANEL OF
CFD1
C WITH MARKED SCREWS
....................................................................... 16
F
IGURE
3.18
B
:
F
RONT AND REAR PANEL OF
CFD8
C WITH MARKED SCREWS
....................................................................... 16
F
IGURE
3.19
B
:
I
NSIDE VIEW OF THE
CFD8
C WITH JUMPER BLOCKS MARKED BY YELLOW CIRCLES
(CFD7
X SIMILAR
) ........ 17
F
IGURE
3.20
B
:
S
IDE PANEL OF
CFD4
C WITH MARKED SCREWS
........................................................................................... 17
F
IGURE
3.21
B
:
O
SCILLOSCOPE TRACES
(
AS IN
F
IGURE
3.8
B LEFT
)
WITH LESS
-
THAN
-
OPTIMAL
CFD
SETTINGS WHICH LEAD
TO PRE
-
TRIGGERING FOR SOME INPUT SIGNALS
.
A
S THE OSCILLOSCOPE IS TRIGGERED BY THE
CFD
TIMING OUTPUT
SIGNAL HERE
,
THE MONITOR OUTPUT TRACES FOR THESE PRE
-
TRIGGER EVENTS
(
MARKED READ ARROW
)
APPEAR
DELAYED COMPARED TO THE PROPERLY TIMED TRACES
.
R
IGHT PICTURE
:
T
IME SUM SPECTRA
(
LINEAR AND LOG
SCALE
)
IN PRESENCE OF PRE
-
TRIGGER EVENTS IN AT LEAST ONE OF THE DELAY
-
LINE
’
S TIMING ELECTRONIC CHANNELS
.
S
IMILAR
“
SIDE PEAKS
”
CAN APPEAR RIGHT OF THE TIME SUM PEAK
(
AT LARGER TIME
)
IF THE
CFD
FOR THE
MCP
SIGNAL PRODUCES PRE
-
TRIGGERS
. ............................................................................................................................... 18
F
IGURE
3.22
B
:
T
YPICAL IMAGE ARTEFACT CAUSED BY PRE
-
TRIGGER EVENTS
(
LEFT PICTURE
).
T
HESE EVENTS MAY APPEAR
ONLY ON CERTAIN PARTS OF THE DETECTOR
:
A
ROUND THE POSITION X
=
13
MM SOME EVENTS SEEM TO BE
“
RELOCATED
”
(
SEE RED ARROW
).
I
F THE TIME SUM
(
AS IN
F
IGURE
3.21
B RIGHT
)
IS PLOTTED AS FUNCTION OF POSITION
(
MIDDLE PICTURE
)
THE LOCALIZED CONTRIBUTION OF PRE
-
TRIGGER EVENTS IS REVEALED
.
S
ETTING A NARROW TIME
SUM GATE CAN REMOVE THE PRE
-
TRIGGER EVENTS BUT THE IMAGE ARTEFACT
(
MISSING DATA
)
REMAINS
,
SEE RIGHT
PICTURE
. ...................................................................................................................................................................... 19
F
IGURE
3.23
B
:
CFD1
X
(
LEFT
)
AND CLOSE
-
UP OF THE
CFD7
X
(
RIGHT
)
SHOWING THE ADDITIONAL INPUT
/
OUTPUT SOCKETS
,
SWITCH AND CONTROL POTENTIOMETERS FOR THE
CFD
X
CIRCUIT
.............................................................................. 20
