What's New?
- Photos of TEL1 at IB2 repairing
December
2003: Fabrication and bench tests of new superconducting and
normal-conducting solenoids for TEL-2 are underway in IHEP(
May
13, 2003: After 2 years of the BBC/TEL studies we got the first indication
of improvement of the 980 GeV Tevatron beam parameters due to operation of
the TEL. Figure on left shows that TEL e-pulse produced by Guassian e-gun
was timed on couple pbar bunches (full strength on one of them) - out of
total 36 antiproton bunches - causing (estimated) tuneshift of
dQ=-(0.002-0.003) at the beginning of high luminosity HEP store #2540. As
the result, the TEL suppressed vertical emittance growth of the bunch
(T:SLASV[32] in Fig on right - measured by Tevatron SyncLite monitor)
while for other bunches #SLASV8 and #SLASV20 in similar beam-beam
conditions but without TEL the growth rate was significantly larger
(0.073mm/hr for A8, 0.040mm/hr for A20, 0.018mm/hr for A32, typical fit
error +-0.008). The emittance growth of weak antiproton bunches is caused
by interaction with strong proton bunches in the Tevatron and is called
"scallops" in the Tevatron jargon. After about 30 min with the
TEL acting on the bunch A33, the electron beam was turned OFF and
emittance growth rate has become the same for all the bunches.
February-March
2003: Working point (tune) scan with new Gaussian electron beam gun has
shown significantly reduced nonlinear beam-beam effects in the interaction
of electron and proton beams. Lifetime of about 160 hours is achieved with
dQ=+(0.003-0.004) that is accetable for trying BBC in the real Tevatron
stores.
- December 31, 2002 - see summary of BBComp accomplishments in 2002 here .
December
2002: Fabrication and bench tests of a new Gaussian electron beam gun are
complete. Profiles and microperveance are found close to simulations. The
gun to be installed during Jan'03 shutdown.
- September, 2002: Six solenoidal coils fabricated at IHEP (Protvino) have arrived to FNAL. The coils will be installed in TEL-1 during 6 week shutdown (tenatatively scheduled to start January 6, 2003) in order to increase B-field in the bends and allow larger range of the TEL beam sizes. The coils to be tested in the E4R building.
August-September,
2002: WP scan with TEL shows very strong dependence of the proton lifetime
vs vertical and betatron frequencies. It is a sign of non-linear beam-beam
resonances. We have started design and fabrication of another e-gun with
Gaussian distribution of the current density which is supposed to ease the
strength of non-linear resonances.
August, 2002: April 2002:
Mikhail Tiunov of Budker INP (
April 2002: Vasily
Parkhomchuk and Vladimir Reva of Budker INP (
Feb.
12, 2002: the first ever operation of the TEL on pbar beam. Found it's not
very different from proton operation except negative sign of the
tuneshift. dQ was about -0.007 (in the Fig - one pbar bunch diplaced
downward by TEL while two others stay untouched.
Since January 2002: TEL-1
is used as a DC beam cleaner when tuned into the Tevatron beam abort gaps
and operate every 7-th turn with some 0.5 A current. So far it's the only
diagnostics of the amont of the DC beam (protons and pbars leaking out of
RF bucket, not captured by the TEV RF system) - see the Fig. - when
e-current L1COLI is turned ON, the total current in the Tevatron IBEAM
shows a kink corresponding to some 2e10 protons lost.
Nov.26,
2001: During 6 weeks shutdown we have replaced FID HV pulser with RF-tube
modulator, stabilized gun solenoid field and performed 1 week long
electron beam studies, e.g., measured ion effects, studied BPM electronics
and software, measured electron beam size and position, used gun
correctors for beam position stabilization in horizontal plane at 60 Hz
(see how stabilization works below - 1 mV =1micron).
- Sept 20, 2001: So far we had total of 10 Tevatron beam study shifts, all with protons only, all but the first one at 980 Gev.
Aug
1-30, 2001: Leonid Tkachenko (IHEP) and Gennady Kuznetsov (BD/BBC) has
considered a modified magnetic system for the second TEL with stronger
B-field in the bend.
June
18-22, 2001, IEEE PAC, Chicago: Nine presentations on the Tevatron
Electron Lens reflect current status of the Beam-Beam Compensation Studies
- see links in Papers.
- June 4, 2001: Internal BD Review of the BBC project (reviewers: M.Church, H.Montgomery, V.Lebedev). Summary: a) good progress so far, especially in shifting the tune; b) decision on fabrication of the 2nd TEl to be taken after demonstration that dQ>0.005 does cause no appreciable drop in lumonosity lifetime; c) BBC group will get 20 more beam study shifts in the Tevatron (in addition to 7 alraedy taken shifts) at the rate of about 3/month.
- May 23, 2001: The FID is in TEL! -Dan Wolff (FID= Fast Ionization Device based HV anode modulator, TEL=Tev El. Lens).
Mar
31, 2001: We have measured tuneshift of 980 GeV protons due to the
electron current in TEL (up to 3.2 A).
Mar 23,
2001: The TEL officially works! We have had the first observation of the
proton tuneshift of about dQ-+0.012, caused by 2.2 A (peak) of electron
current in the TEL (this is on 150 GeV protons).
Mar.
2001: The first TEL (there is a second one being considered already) is
installed
in the Tevatron tunnel (sector F48). Electrical work is commencing.
Jan.
2001: A new liquid helium bypass was installed in the Tevatron tunnel at
F48 (the eventual location for the TEL). Nothing is stopping us from
moving the magnet setup very soon.
Dec.
2000: We studied beam properties in the TEL with wire mesh screens.
The 8-kV pulse modulator was set up to run up to 3.25 A (peak) current and up to 50 kHz rep rate.
Nov.
2000: The residual gas in the vacuum glowed when the beam passed through
it. The ghostly blue was difficult to capture on film, however.
The entire contraption was baked in place for the first time. This eliminated any noticeable residual gas glowing. The following picture is looking at the gun, with the "downstream" part further back.
- Oct. 2000: The magnets are
finally completely assembled in our "staging area," and magnetic
measurements have commenced.
To see our results, please check out the following papers (word documents):
Magnetic System (FNAL-Conf-00/337 (2000))
Magnetic Measurements (FNAL-Conf-00/338
(2000))
- Sept 13, 2000: After one quench, we successfully reached 5.64 T in the first high current test of the SC solenoid. The next morning, a second quench took place at 6.6 T. After that, we were unable to quench the solenoid (up to 6.7 T) at the faster ramp rate of 30 A/s (maximum allowed by the power supply). The magnet quenches very quietly and does not consume much of He at the quench. That's good.
Sept
3, 2000: The superconducting solenoid finally successfully cooled down to
4.5 K!
Even the meter thinks the resistance is roughly zero.
Aug.
2000: Ed Beebe and Sasha Pikin of Brookhaven (pictured with Sergei Kozub
of IHEP) visited the BBComp group.
The new electron gun was tested, and various parameters of the electron beam were examined. This cool picture was pilfered by Fermilab publicity office as a "physics-ish" picture in some brouchures!
The 6.5 T superconducting solenoid arrives from Protvino (
Jul.
2000: The new electron gun is completed!
The design was for a high-perveance, convex-cathode gun, and it was designed and fabricated here at Fermilab.
At EPAC 2000, some of the group published this three-page paper.
Christina Dimopoulou of C Jun. 2000: Dmitry Shatilov of Budker INP visits the group in order to study various
beam-beam simulations for the Tevatron with the planned TEL.
Apr. 2000:
Alex Martinez visits IHEP to inspect the TEL cryostat fabrication.
This is to house the superconducting main solenoid on the final assembly (pictured with
Mar. 2000:
Nikolay Solyak visits IHEP (Protvino) to inspect fabrication of TEL magnets.
Picture shows S. Kozub, N. Solyak, and V. Sytnik.
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