Operation
Diagnostics System
System for
for
Operation of
of the
the Beam
Beam Diagnostics
Tevatron
Lens
Tevatron Electron
Electron Lens
X.Zhang, K.Bishofberger*, J.Fitzgerald, G.Kuznetsov, M.Olson,
X.Zhang, K.Bishofberger*, J.Fitzgerald, G.Kuznetsov, M.Olson,
A.Semenov,
N.Solyak
A.Semenov, V.Shiltsev,
V.Shiltsev, N.Solyak
PO Box 500, FNAL, Batavia, IL 60510
PO Box 500, FNAL, Batavia, IL 60510
*University of California at Los Angeles, P.O. Box 951547, Los Angeles, CA 90095-1547
^University of California at Los Angeles, P.O. Box 951547, Los Angeles, CA 90095-1547
Abstract. The first Tevatron Electron Lens (TEL) has been installed and commissioned
Abstract. The first Tevatron Electron Lens (TEL) has been installed and commissioned
successfully
project at
at Fermilab[l].
Fermilab[1]. Currently
Currentlyititisis
successfully as
as part
part of
of the
the Beam-Beam
Beam-Beam Compensation
Compensation project
operated
routinely
for
DC
beam
cleaning
during
Tevatron
luminosity
stores
and
foradvanced
advanced
operated routinely for DC beam cleaning during Tevatron luminosity stores and for
beam-beam
electron and
and proton
proton (antiproton)
(antiproton)beam
beamdiagnostics,
diagnostics,
beam-beam studies.
studies. This
This paper
paper reviews
reviews the
the electron
which
waveform, losses,
losses, position,
position, timing
timingand
andprofile.
profile.InIn
which allow
allow us
us to
to measure
measure beam
beam intensity,
intensity, waveform,
addition,
available from
from the
the Tevatron
Tevatron control
control system,
system,
addition, other
other proton
proton (antiproton)
(antiproton) diagnostics,
diagnostics, available
which
are
used
for
tuning
beam
parameters
in
the
TEL
(tune-shift,
orbit,
emittances,
lifetime
which are used for tuning beam parameters in the TEL (tune-shift, orbit, emittances, lifetime
measurements,
present the
the results
results of
ofmeasurements
measurementsofofthe
thebeam
beam
measurements, etc)
etc) are
are also
also described.
described. We
We also
also present
parameters
and
discussions
for
future
upgrades.
parameters and discussions for future upgrades.
11BEAM
MONITORING
BEAM POSITION
POSITION MONITORING
We
electrodes in
in the
the TEL
TEL system
systemnear
neareach
eachend
end
Wehave
have installed
installed two
two pairs
pairs of
of pickup
pickup electrodes
ofofthe
us to
to measure
measure horizontal
horizontal and
andvertical
verticalpositions
positionsofof
theinteraction
interaction region
region that
that enables
enables us
electron,
and exiting
exiting the
the TEL.
TEL. Each
Eachpickup
pickup
electron, proton
proton and
and antiproton
antiproton beams
beams entering
entering and
electrode
cylinder with
with aa diameter
diameterofof70mm
70mmand
andcut
cut
electrode pair
pair isis made
made of
of aa stainless
stainless steel
steel cylinder
diagonally
the BPM
BPM pickup
pickup electrodes
electrodesare
areshown
shownbelow
belowinin
diagonally in
in half.
half. The
The TEL
TEL layout
layout and
and the
Figure
Figure1.1.
Superconducting
^/
solenoid
__
Pt
#2 jr^ft . w ! re .P^Al"..
|2
.Pt
P
FIGURE 1.
1. Layout
Layout of
of the
the TEL
TEL (Px,
(Px, Py
FIGURE
Py are
are the
the beam
beamposition
positionpickup
pickupelectrodes)
electrodes)
CP648, Beam Instrumentation Workshop 2002: Tenth Workshop, edited by G. A. Smith and T. Russo
2002 American Institute of Physics 0-7354-0103-9
483
We have a broadband three-beam BPM system, which is used to measure proton,
antiproton, and electron beam positions. The requirement for beam position accuracy
is 50µm
50|im rms with an electron-(anti)proton position difference
difference less than 100µm.
lOOjim.
The three-beam BPM system[2]
system [2] is composed of aa LabVIEW
Lab VIEW application
application program
program
operating on a Macintosh computer utilizing aa digital
digital oscilloscope for data acquisition.
The four position detectors are
are sequentially
sequentially connected to the oscilloscope's
oscilloscope's inputs
through the RF Multiplexer. The computer communicates with the oscilloscope and
the multiplexer and links with Tevatron Accelerator Controls Network(ACNET). A
Beam Synchronous pulse generated by a Camac 279 module
module triggers the
the scope’s
scope's main
sweep. The oscilloscope must be operated in the delay trigger mode to obtain the finer
timing resolution required to capture the 20 ns bunch
bunch signal.
signal. The
The delay
delay must be
adjusted properly for each position detector to compensate for differences
differences in cable
adjusted
lengths and beam flight times. The default delays for the oscilloscope trigger are
automatically set from
from a look-up table, depending upon the selected bunch and BPM
detector, and have been empirically determined to trigger the oscilloscope about 10 ns
before a given bunch arrives.
When the beam traverses the detector, it generates a doublet current signal similar
to Figure 2 on each plate of the same detector. Then both signals are digitized to 500
points by the oscilloscope and transferred to the computer through
through the
the GPIB
GPIB interface.
The vertical scale of the oscilloscope can also be changed to improve the performance
according to the bunch intensity.
Trig'd
\J
Scope sweep time (ns)
(a)
(a)
(b)
FIGURE 2. Doublet signal from pickup electrode (a)
(a) antiproton pulse and
and (b)
(b) electron
electron pulse
pulse
To calculate the beam position, the digitized doublet signal of each pickup plate is
first
128-512 times by the scope to minimize noise. Next the signal strength
first averaged 128~512
of the two plates is determined by digitally integrating the signals individually.
Finally,
Finally, a difference
difference over
over sum calculation is performed
performed to obtain a position reading.
The above process repeats until all four proton and all four antiproton
antiproton beam
beam positions
positions
have been obtained.
484
To obtain the integral of the signal strength, several methods were tested. We first
tried a zero-crossing method, where the most positive and most negative points of the
averaged traces are found, and a cubic polynomial is fit to the data between them to
find the zero-crossing point. Then the signal is rectified by multiplying all points after
the zero-crossing with -1. The advantage of the above procedure over a simple
addition is that the effect of offset, noise, ringing, or satellite bunch signals outside the
central bunch is greatly reduced. The signal strength of each plate is then determined
by digitally integrating the rectified signals individually. In addition, a software BandPass filter can be applied to optimize the signal-to-noise ratio. However, the distorted
waveform creates an error in the zero crossing and hence an error of the reported beam
position. This method works poorly for the electron beam, since the electron beam
pulse has a 30MHz modulation coming from the high-voltage modulator circuits, and
its shape also makes it very difficult to find the correct zero crossing. (Figure 2(b)).
The second method is trying to find the averaged peak value of the traces.
Unfortunately the peak has a small signal-to-noise ratio, giving a larger error in beam
position readings. This is especially true for electron beams.
The third method is taking the absolute value of the averaged traces and
integrating. The software Band-Pass filter can still be applied to optimize the signalto-noise ratio. This method is relatively easy and fast and gives a satisfying answer.
We use it mostly.
Typically, we calibrate the BPM readings by moving the electron beam transversely
with magnetic steering coils. Figure 3(a) shows the measurement of the linearity of
one pair of electrodes made with the electron beam, which is quite satisfactory in the
range of ±6 mm around centerline (the BPM pickup pipe diameter is 70 mm). By this
way, we can also get the calibrated coefficient of the BPM system.
1.0-
Calibration of the TEL BPM
0.8-
(using VC1, HC2=0, lb=2A, Bm/Bg=35KG/3.7KG)
y = 0.9973X + 0.031
4
R2 = 0.9965
^^+
^***^^
^*^<^^
^^^
-ft
-
8
-
4
0
4
8
Calculated Beam Position (mm)
20
40
60
80
100
Pulse full width (ns)
(a)
(b)
FIGURE 3. (a) The linearity measurement of the BPM. (b) Measured beam position vs. beam pulse
width on a BPM test stand
A lot of effort has been taken to reach our goal of high resolution and small error
for beam position. Besides increasing the number of averages, we improved the
vacuum feedthroughs with SMA connectors instead of simple solder-on pins, which
led to a substantial reduction of mismatch and ringing. Using 128 averages and full
485
scope bandwidth, a beam resolution of about 30|im rms was achieved for a 2A peak
current of 800ns-long electron pulse. An rms resolution of 50|im was obtained for a
single proton bunch with the intensity of 9.4xl010, and the antiproton resolution was
about 90|im rms, which was over ten times weaker.
However, the most serious problem comes from the discrepancy between the
electron beam position and proton beam position readings. One source of the offset
comes from the difference in the channels of the oscilloscope. To solve this, we use
the same channel to read both plates of the same BPM pair by switching inputs via the
multiplexer. We also improved the beam synchrotron signal to scope trigger to reduce
the mis-triggering. By doing these, we eliminated an offset of 0.3mm. However, the
major source of the offset comes from the different BPM impedances for electron
beam and proton beam signals, since for proton-like signal the main frequency
component is about 53MHz while for electron beam the main frequency component is
less than 2MHz. The capacitance between the two plates and the cross-talking between
pairs of electrodes might also contribute to the offset. The maximum offset between
electron beam and proton beam is over 1mm (see Figure 3(b)). This makes it very
difficult to align the electron beam exactly to the proton beam orbit.
To minimize the offset, various software and analog filters were tested. In the end,
a 5MHz software low pass filter was used, which decreased the average position
difference to 0.3mm. Thereafter during the electron beam colliding with the proton
bunch, a fine-tuning of the beam alignment was carried out ad hoc by maximizing tune
shift and minimizing the proton beam loss.
As a part of the TEL upgrading plan, new stripline electrodes will replace the
current arrangement in summer of 2002. This will decrease cross-talking, flatten
frequency response, increase the sensitivity and be better calibrated initially. We hope
we can achieve a better beam position resolution and lower the offsets to less than
100jim in future.
2 ELECTRON BEAM QUALITY MONITORS
We have installed electron beam quality monitors which measures the electron
beam current, beam profile, current stability, and beam pulse shape.
2.1 Electron Beam Profile Monitor
Beam profile is a crucial characteristic of the electron lens. For linear beam-beam
compensation the electron beam should have a profile with uniform charge
distribution. For future non-linear beam-beam compensation, the electron beam is
required to have a charge distribution closer to the Gaussian distribution.
To measure the electron beam profile, two wire scanners, one horizontal and one
vertical, are installed in the TEL near the center of the main solenoid. Wires can be
moved in or out of the beam pipe by remotely controlled stepping motors. In normal
Tevatron operation, they are moved completely out of the beam orbit in order not to
disturb the beams. The geometry of the wire is shaped like a "fork". The distance
between the fork claws is 15mm, from the wire to top edge is 22mm, the wire
486
diameter is 100µm,
diameter
lOOjim, and the beam pipe diameter is 70mm.
70mm. Moreover,
Moreover, the
the dimensions
dimensions
give us
us aa good scale for calibration of steering
give
steering strength
strength of
of correctors
correctors for
for the
the electron
electron
beam and
and in
in turn,
turn, to
beam
to calibrate
calibrate the
the pickup
pickup BPM
BPM systems.
systems.
By steering
steering the
the electron
electron beam
beam vertically
vertically or
By
or horizontally
horizontally by
by aa known
known amount
amount we
we can
can
scan the
the beam
beam across
across the
the wire.
wire. The
scan
The portion
portion of
of the
the beam
beam intercepted
intercepted by
by the
the wire
wire gives
gives aa
sliced X
X (or
(or Y)
Y) beam
beam profile
profile as
sliced
as shown
shown in
in Figure
Figure 4(a).
4(a). Then
Then the
the radial
radial beam
beam profile
profile can
can
be restored
restored assuming
assuming almost
almost radial
radial symmetry.
be
symmetry. This
This restored
restored beam
beam profile,
profile, also
also in
in
Figure 4(a),
4(a), indicates
indicates aa mostly
mostly flattop
flattop profile
Figure
profile with
with somewhat
somewhat less
less charge
charge in
in the
the center
center
than around
around the
the edge.
edge. This
This is
is caused
caused by
the electron
than
by the
electron space
space charge
charge effect
effect (the
(the electrons
electrons
in the
the center
center are
are moving
moving slower
slower than
than those
those in
in
in the
the edge).
edge). The
The beam
beam diameter
diameter is
is about
about
3.5mm. The
The restored
restored profile
profile is
3.5mm.
is in
in good
good agreement
agreement with
with the
the two-dimensional
two-dimensional electron
electron
current profile
profile (Figure
(Figure 4(b)),
4(b)), previously
previously measured
measured by
current
by aa “pinhole”
"pinhole" collector
collector scanner
scanner on
on
testbed[3]. This
This collector
aa testbed[3].
collector simply
simply has
has aa very
very small
small hole
hole that
that allows
allows aa small
small fraction
fraction of
of
the current
current to
to pass
pass and
and be
be measured.
measured. Scanning
the
Scanning in
in two
two dimensions
dimensions allows
allows for
for detailed
detailed
profile measurements.
measurements.
profile
(b)
(a)
(a)
=2A).
FIGURE 4.
4. (a)
FIGURE
(a) 1-D
1-D and
and (b)
(b) 2-D
2-D beam
beam profiles
profiles (I
(Ipeak
peak=2A).
Unfortunately, both
both wires
wires in
Unfortunately,
in the
the TEL
TEL have
have burnt
burnt out
out recently.
recently. Due
Due to
to aa major
major
upgrade
in
summer
2002,
there
will
be
no
room
for
the
wire
apparatus.
Instead,
upgrade in summer 2002, there will be no room for the wire apparatus. Instead, rightrightangled "knives"
“knives” will
will be
be installed
installed near
near the
angled
the beam
beam pipe
pipe wall.
wall. The
The electron
electron beam
beam will
will be
be
scanned through
through the
the knives
knives to
to measure
measure the
scanned
the profile.
profile.
2.2 Electron
Electron Beam
2.2
Beam Current
Current and
and Charge
Charge Monitors
Monitors
The electron
electron beam
beam current
The
current is
is measured
measured by
by wideband
wideband current
current transformers
transformers both
both atat
the
cathode
and
collector.
They
monitor
the
electron
beam
pulse
shapes
as
well
the cathode and collector. They monitor the electron beam pulse shapes as well as
as the
the
beam
loss
through
the
TEL
system.
Typical
output
waveforms
are
shown
in
Figure
beam loss through the TEL system. Typical output waveforms are shown in Figure
2(b) and
and 5.
5.
2(b)
The
electron
beam charge
The electron beam
charge monitor
monitor uses
uses common
common BPM
BPM pickup
pickup electrodes.
electrodes. An
An RF
RF
switch is used to switch the signals between the BPM electronics and the charge
switch is used to switch the signals between the BPM electronics and the charge
monitor. There are four sets of identical electronics, each for one of the four pairs of
monitor. There are four sets of identical electronics, each for one of the four pairs of
BPM detectors. The charge amplifiers are used to get the electron beam charge
BPM detectors. The charge amplifiers are used to get the electron beam charge
487
distribution along
distribution
along the
the beam
beam pulse.
pulse. The
The lower
lower curve
curve of
of Figure
Figure 55 shows
shows aa typical
typical signal
signal
from one
one channel
charge monitor,
monitor, which
from
channel of
of the
the electron
electron charge
which is
is dependent
dependent on
on the
the beam
beam
position. By
By adding
adding up
up both
both channels
channels from
position.
from the
the same
same pair
pair of
of pickup
pickup electrodes,
electrodes, we
we can
can
get the
the total
total charge
charge of
of the
the electron
electron beam
beam independent
independent of
the beam
beam position.
position.
get
of the
Chl Max
2.09 V
Ch3 High
1,79V
FIGURE 5.
5. The
FIGURE
The lower
lower trace
trace taken
taken from
from one
one channel
channel of
of the
the charge
charge monitor,
monitor, the
the small
small dent
dent in
in the
the lower
lower
waveform is
is the
the proton
proton bunch
bunch signal,
waveform
signal, which
which is
is timed
timed during
during the
the flat
flat part
part of
of the
the electron
electron pulse.
pulse.
The charge
charge amplifiers
The
amplifiers have
have aa saturation
saturation threshold
threshold and
and we
we have
have to
to be
be careful
careful with
with
the input
input signal.
in most
most cases,
the
signal. Fortunately,
Fortunately, in
cases, the
the electron
electron current
current is
is not
not so
so high
high as
as to
to
overfeed the
the system.
system. This
This system
system can
can also
also be
be used
used to
to measure
overfeed
measure the
the electron
electron beam
beam
position. It
be further
further upgraded
position.
It will
will be
upgraded by
by fine
fine synchronizing
synchronizing signals
signals from
from both
both pickup
pickup
electrodes
and
digitizing
to
enable
the
data
to
be
shared
over
ACNET.
electrodes and digitizing to enable the data to be shared over ACNET.
We are
We
are also
also prototyping
prototyping an
an electron-current
electron-current stability-measuring
stability-measuring system.
system. It
It has
has two
two
channels,
with
a
14-bit
fast
ADC
(AD6644)
and
a
262Kx18-bit
high-speed
channels, with a 14-bit fast ADC (AD6644) and a 262Kxl8-bit high-speed FIFO
FIFO
memory (IDT72V2105)
memory
(IDT72V2105) each
each channel.
channel. This
This allows
allows the
the system
system to
to sample
sample and
and acquire
acquire
data
at
speeds
up
to
66MHz
and
up
to
data
record
lengths
of
512K.
There
data at speeds up to 66MHz and up to data record lengths of 512K. There are
are two
two
modes of
of operation:
operation: continuous
modes
continuous mode
mode and
and gated
gated mode.
mode. In
In continuous
continuous mode,
mode, the
the
digitizer samples
samples and
digitizer
and writes
writes continuously
continuously at
at aa rate
rate of
of 66MSPS
66MSPS to
to FIFO
FIFO memory
memory until
until
full. In
In gated
gated mode,
mode, the
full.
the digitizer
digitizer only
only samples
samples signals
signals that
that we
we want
want and
and writes
writes to
to the
the
FIFO. In
In each
each case,
case, 7.6ms
7.6ms of
of data
data will
be recorded
recorded with
time resolution
FIFO.
will be
with aa time
resolution 15ns.
15ns. In
In
addition, the
the threshold,
addition,
threshold, delay,
delay, and
and window
window parameters
parameters for
for the
the gating
gating can
can be
be
preprogrammed and
preprogrammed
and the
the gating
gating rate
rate can
can be
be as
as low
low as
as 1Hz.
IHz. Using
Using the
the cathode
cathode current
current or
or
charge intensity
monitor as
that
the
stability
of
the
charge
intensity monitor
as the
the input,
input, preliminary
preliminary results
results show
show
that
the
stability
of
the
-3
electron beam
beam current
current from
electron
from pulse
pulse to
to pulse
pulse was
was about
about 3.6×10
3.6xlO~3 at
at 2.5A
2.5A peak
peak current.
current.
33 (ANTI)PROTON
(ANTI)PROTON DIAGNOSTICS
DIAGNOSTICS
Besides the
the BPM
BPM system
of the
the TEL,
TEL, we
we also
also use
use the
the beam
beam diagnostics
diagnostics of
of the
the
Besides
system of
Tevatron to
to monitor
monitor proton
Tevatron
proton and
and antiproton
antiproton parameters,
parameters, which
which include
include intensity,
intensity,
emittance, orbit,
orbit, lifetime,
emittance,
lifetime, and
and tune[4].
tune[4]. We
We are
are also
also able
able to
to monitor
monitor the
the luminosity
luminosity and
and
488
the
which is
is disseminated
disseminated by
by the
the CDF
CDF detector.
detector. The
The
the proton
proton losses
losses bunch-by-bunch,
bunch-by-bunch, which
tunes
are
measured
by
Shottky
spectra
analyzers,
whose
output
appears
in
Figure
6(a).
tunes are measured by Shottky spectra analyzers, whose output appears in Figure 6(a).
In
in the
the Tevatron.
Tevatron. The
The spectrum
spectrum in
in
In this
this example,
example, there
there were
were only
only two
two proton
proton bunches
bunches in
the
left
part
shows
the
tune
of
the
typical
bunch
that
is
not
colliding
with
the
electron
the left part shows the tune of the typical bunch that is not colliding with the electron
beam,
shifted tune
tune of
of the
the other
other bunch
bunch colliding
colliding with
with the
the
beam, but
but the
the right
right part
part shows
shows the
the shifted
electron
spectra heavily
heavily together
together with
with the
the proton
proton loss
loss monitor
monitor
electron beam.
beam. We
We rely
rely on
on these
these spectra
in
beam orbit.
orbit. Our
Our goals
goals are
are to
to
in order
order to
to fine-tune
fine-tune the
the electron
electron beam
beam onto the proton beam
maximize
maximize the
the tuneshift
tuneshift while minimizing any proton losses.
A
commissioned. The
The beam
beam
A new
new bunch-by-bunch
bunch-by-bunch tune meter[5] is currently being commissioned.
emittances
flying wire systems[6],
systems [6], which have errors
errors of
of about
about
emittances are
are measured by the flying
10%.
monitor will
will give
give us
us aa
10%. We
We expect
expect that the recently upgraded synchrotron light monitor
double-check
and
allow
us
to
monitor
the
proton
or
antiproton
emittance
variations
double-check and
antiproton emittance variations
continuously
studies [7]. Also
Also the
the beam
beam lifetime
lifetime isis
continuously during
during beam-beam compensation studies[7].
monitored
by
the
Fast
Beam
Integrator
(FBI),
which
relies
on
the
wall
current
monitored by the Fast
on the wall current
monitor
[4].
monitor[4].
A
with the
the proton
proton bunch
bunch isis by
by
A very
very accurate
accurate method
method of aligning the electron beam with
means
orbit. We
We do
do this
this by
by modulating
modulating the
the electron
electron
means of
of 'tickling'
‘tickling’ the proton beam orbit.
beam
for precise
precise centering
centering of
of the
the
beam current[l].
current[1]. That method provides us the information for
electron
beam. The
The Tevatron
Tevatron orbit
orbit measurement
measurement
electron beam
beam onto
onto the proton
proton (or antiproton) beam.
system
micrometers, which
which helps
helps us
us to
to double
double check
check the
the our
our
system has
has aa resolution
resolution of 150 micrometers,
BPM
BPM measurement.
measurement.
0.720.70"§• 0.68-
I 0.64lS 0.62U 0.60-
I o.58:
*~ 0.560.54 0.580
0.585
0.690
0
Fractional tune unit
5
10
15
20
25
30
35
Electron-Proton Colliding Elapse Time (min)
(a)
(a)
(b)
(b)
FIGURE 6.
6. (a)
(a) Tuneshift
Tuneshift due
FIGURE
due to
to colliding
colliding with
with electron
electron beam
beam
(b) Proton
Proton beamsize
beamsize during
(b)
during the
the collision
collision with
with electron
electron beam
beam
Figure 6(b)
6(b) shows
shows the
the proton
proton beam
Figure
beam size
size measured
measured over
over time
time while
while colliding
colliding with
with the
the
electron beam
beam by
by Tevatron
Tevatron flying
flying wires.
wires. Since
Since the
the electron
electron beam
electron
beam had
had aa hollow
hollow shape,
shape,
the non-linearity
non-linearity of
of the
the electron
electron beam
beam edge
edge is
the
is very
very strong.
strong. Therefore,
Therefore, the
the tail
tail of
of the
the
proton bunch
bunch was
was scraped
scraped off,
off, leaving
leaving the
the major
major part
proton
part of
of the
the proton
proton beam
beam which
which can
can fit
fit
into the
the electron
electron beam
beam comfortably.
comfortably. In
In this
this measurement,
measurement, the
into
the initial
initial proton
proton beam
beam sizes
sizes
were larger
larger than
than the
the design
design value.
value. But
But the
the equilibrium
equilibrium beam
beam sizes
were
sizes correspond
correspond to
to the
the
electron
beam
acceptance
of
20~25π
mm•mrad,
which
is
what
the
TEL
is
designed
electron beam acceptance of 20~257i mm»mrad, which is what the TEL is designed toto
accommodate. The
The coming
coming upgrade
accommodate.
upgrade of
of the
the TEL
TEL will
will decrease
decrease the
the bend
bend angle
angle of
of the
the
electron
beam
from
90°
degrees
to
about
60°
degrees,
and
more
solenoids
will
electron beam from 90° degrees to about 60° degrees, and more solenoids will be
be
489
added in the bend to minimize the electron beam size in the bends. Also a new electron
gun with a parabolic beam profile will be installed in order to eliminate the sharp edge
and compensate the hollow in the electron beam profile. By doing these, we hope that
we will be able to vary the beam size by a factor of two and also increase the electron
beam acceptance significantly.
4 CONCLUSION
The TEL is a very important project for Tevatron upgrading. It is not only working
as a setup for advanced beam-beam studies, but also being operated routinely as the
Tevatron DC beam cleaner. Occasionally a troublesome DC beam is generated in the
Tevatron, which causes a spiky background in the CDF and sometimes quenches
during aborting. The beam diagnostic systems for the TEL electron lens played a
crucial role in commissioning. We were able to measure the electron beam parameters.
We also have successfully aligned the electron beam to the proton beam and obtained
excellent beam tune shift. The BPM offset issues between the electron beam and the
proton beam have not allowed us to quickly align the electron beam to the proton
beam, but a new system will be installed in the coming months that will deliver huge
improvements. At the same time, substantial efforts are being put into further
improvements on other beam diagnostics in order to secure the successful operation of
the TEL in future.
ACKNOWLEDGMENTS
We thank Jim Crisp, Jim Steimel, Dan Wolff, Dave McGinnis, Howard Pfeffer and
David Peterson for their helpful advice and discussions on BPM issues. We also thank
Stephen Pordes and Wim Blockland for their help using their flying wire system for
proton size measurement, Dean Still with the Tevatron Schottky tune measurement
and C.Y. Tan for his advices on the tune-meter system. Finally we thank the
Accelerator Controls Department for their help for the TEL control system and the
Tevatron operation crew and during TEL studying shifts.
REFERENCES
1.
2.
3.
4.
5.
6.
7.
V.Shiltsev et al, submitted to PAC2001
M. Olson, A. A. Hahn, AIP conference proceedings 390, pp. 468-475, Argonne fl., May 1996
A. Shemyakin, et al, Proc.of EPAC 2000, p.1271
Tevatron Run n Handbook, Chapter 6.12, http://www-runii.fnal.gov/
C.Y. Tan, FERMILAB-TM-2078, 2000
J. Gannon et al, FERMILAB-CONF-89/64, 1989
A.A. Hahn, HEACC'92, pp. 248-250
490