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B. J. Holzer et al.
challenges. The kicker voltage was obtained by periodically extending the pickup
signal, passing it through narrow band filters spaced by 200 MHz (1/5 ns) and driving individual cavities. Taming coherent lines while meeting timing requirements
was a serious challenge [148]. When all was said and done the cooling system
increased the integrated luminosity of uranium-uranium collisions by a factor of
five and typically doubled the gold-gold luminosity.
At Fermilab, OSC is being pursued at the IOTA facility [149]. In OSC a particle
emits electromagnetic radiation in the first (pickup) wiggler. Then, the radiation
amplified in an optical amplifier (OA) makes a longitudinal kick to the same particle
in the second (kicker). A magnetic chicane is used to make space for the OA and
to delay a particle so that to compensate for a delay of its radiation in the OA
resulting in simultaneous arrival of the particle and its amplified radiation to the
kicker wiggler. The chosen optical wavelength is 800 nm, resulting in bandwidths
approaching 10 14 Hz. In the proposed test, the use of 100-MeV (γ = 200) electrons
instead of protons greatly reduces the cost of the experiment but does not limit its
generality and applicability to hadron colliders. Conceptual design of the system is
complete, with engineering design of the wiggler and optical hardware underway.
Already in late 1970s the need for “stochastic stacking” has been realized [150].
In the “old” CERN AA (antiproton accumulator) [151] early stacking methods were
tested and applied in routine operation. In the CERN AAC (antiproton accumulator
complex) [152] the antiprotons (pbar or p) coming from the AC (collector ring)
were transferred to the inner ring (AA = accumulator). There dedicated stack tail
and stack core systems took over the antiprotons after they have passed a precooling system in the AA and were transferred to another orbit by means of RF
manipulations. At Fermilab [138] stacking is done in the accumulator ring and later
also in the recycler. For the future stacking with stochastic cooling is planned in the
frame of the FAIR project [110]. Stochastic stacking of rare radioactive ions has
been considered during the planning phase of RIKEN [110] upgrades between 1900
and about 2000 and for FAIR [110].
At Fermilab huge progress has been made since the year 2000 [153], this
includes stacking with stochastic cooling was done in three separate machines.
The debuncher [154], which accepted ~1.5 × 10 8 antiprotons every 2.1 s, used the
McGinnis waveguide directional couplers in eight bands over the frequency range
4–8 GHz for a factor of 10 reduction in longitudinal and transverse size. A key
piece was the implementation of ramping the amplifier gain down during the cycle,
to counter act noise to signal for the momentum bands in the notch filters. A 6 dB
decrease in gain resulted in a 12% decrease in the 95% momentum width after 2 s
of cooling. The Accumulator [154] accepted the same ~1.5 × 10 8 antiprotons and
used the Palmer method to build a ‘stack’. Peak performance reached 2.6 × 10 11
antiprotons in an hour, with regular transfers to the Recycler to mitigate the known
decrease in performance with larger stacks. The Recycler, using a combination of
stochastic and electron cooling [155], reached intensities of greater than 4 × 10 12
regularly, with peak intensity of 6.1 × 10 12 and delivering over 4 × 10 13 per week
to the collider program.
B. J. Holzer et al.
challenges. The kicker voltage was obtained by periodically extending the pickup
signal, passing it through narrow band filters spaced by 200 MHz (1/5 ns) and driving individual cavities. Taming coherent lines while meeting timing requirements
was a serious challenge [148]. When all was said and done the cooling system
increased the integrated luminosity of uranium-uranium collisions by a factor of
five and typically doubled the gold-gold luminosity.
At Fermilab, OSC is being pursued at the IOTA facility [149]. In OSC a particle
emits electromagnetic radiation in the first (pickup) wiggler. Then, the radiation
amplified in an optical amplifier (OA) makes a longitudinal kick to the same particle
in the second (kicker). A magnetic chicane is used to make space for the OA and
to delay a particle so that to compensate for a delay of its radiation in the OA
resulting in simultaneous arrival of the particle and its amplified radiation to the
kicker wiggler. The chosen optical wavelength is 800 nm, resulting in bandwidths
approaching 10 14 Hz. In the proposed test, the use of 100-MeV (γ = 200) electrons
instead of protons greatly reduces the cost of the experiment but does not limit its
generality and applicability to hadron colliders. Conceptual design of the system is
complete, with engineering design of the wiggler and optical hardware underway.
Already in late 1970s the need for “stochastic stacking” has been realized [150].
In the “old” CERN AA (antiproton accumulator) [151] early stacking methods were
tested and applied in routine operation. In the CERN AAC (antiproton accumulator
complex) [152] the antiprotons (pbar or p) coming from the AC (collector ring)
were transferred to the inner ring (AA = accumulator). There dedicated stack tail
and stack core systems took over the antiprotons after they have passed a precooling system in the AA and were transferred to another orbit by means of RF
manipulations. At Fermilab [138] stacking is done in the accumulator ring and later
also in the recycler. For the future stacking with stochastic cooling is planned in the
frame of the FAIR project [110]. Stochastic stacking of rare radioactive ions has
been considered during the planning phase of RIKEN [110] upgrades between 1900
and about 2000 and for FAIR [110].
At Fermilab huge progress has been made since the year 2000 [153], this
includes stacking with stochastic cooling was done in three separate machines.
The debuncher [154], which accepted ~1.5 × 10 8 antiprotons every 2.1 s, used the
McGinnis waveguide directional couplers in eight bands over the frequency range
4–8 GHz for a factor of 10 reduction in longitudinal and transverse size. A key
piece was the implementation of ramping the amplifier gain down during the cycle,
to counter act noise to signal for the momentum bands in the notch filters. A 6 dB
decrease in gain resulted in a 12% decrease in the 95% momentum width after 2 s
of cooling. The Accumulator [154] accepted the same ~1.5 × 10 8 antiprotons and
used the Palmer method to build a ‘stack’. Peak performance reached 2.6 × 10 11
antiprotons in an hour, with regular transfers to the Recycler to mitigate the known
decrease in performance with larger stacks. The Recycler, using a combination of
stochastic and electron cooling [155], reached intensities of greater than 4 × 10 12
regularly, with peak intensity of 6.1 × 10 12 and delivering over 4 × 10 13 per week
to the collider program.