The design of the region close to the interaction point of the FCC-ee experiments is especially c... more The design of the region close to the interaction point of the FCC-ee experiments is especially challenging. The beams collide at an angle (+-15 mrad) in the high-field region of the detector solenoid. Moreover, the very low vertical beta_y* of the machine necessitates that the final focusing quadrupoles have a distance from the IP (L*) of around 2 m and therefore are inside the main detector solenoid. The beams should be screened from the effect of the detector magnetic field, and the emittance blow-up due to vertical dispersion in the interaction region should be minimized, while leaving enough space for detector components. Crosstalk between the two final focus quadrupoles, only about 6 cm apart at the tip, should also be minimized.
A crucial part of the design of an FCC-ee detector is the minimisation of the disruption of the b... more A crucial part of the design of an FCC-ee detector is the minimisation of the disruption of the beam due to the presence of a large and powerful detector magnet. Indeed, the emittance blow-up of the few meters around the interaction point (IP) at lower energies is comparable to the emittance introduced by the rest of the 100 km ring. Vertical emittance is the single most important factor in achieving high performance (luminosity, in this case) in a modern e^+ e^- storage ring such as the FCC-ee. The design adopted is the simplest possible arrangement that can nevertheless deliver high performance: two additional coils per IP side. The performance achieved is such that vertical emittance blow-up will not be a limiting performance factor even in the case of a ring with four experiments, and even in the most demanding energy regime, that of the Z running (about 45 GeV beam energy).
We discuss a novel coherent beam-beam instability in collisions with a large crossing angle. The ... more We discuss a novel coherent beam-beam instability in collisions with a large crossing angle. The instability appears in the correlated head-tail motion of the two colliding beams. Cross wake force is introduced to represent the head-tail correlation between colliding beams. The cross wake force is localized at the collision point. Mode coupling theory based on the cross wake force is developed. Collision scheme with a large crossing angle is being very popular in design of electron positron collider. In SuperKEKB project, a collision with a large crossing angle is performed to boost the luminosity 0.8×1036 cm−2s−1. Future circular collider, FCC is also designed with a large crossing angle. Strong-strong simulations have shown a strong coherent head-tail instability, which can limit the performance of proposed future colliders. The mode coupling theory using the cross wake force explains the instability. The instability may affect all colliders designs based on the crab waist scheme.
A strong candidate for the Standard Model Scalar bo son, H(126), has been discovered by the Large... more A strong candidate for the Standard Model Scalar bo son, H(126), has been discovered by the Large Hadro n Collider (LHC) experiments. In order to study this fundamental particle with unprecedented precision, and to perform precision tests of the closure of the Stand ard Model, we investigate the possibilities offered by an ee storage ring collider. We use a design inspired by the B-factori es, taking into account the performance achieved at LEP2, and imposing a synchrotron radiation power limit of 100 MW. At the most relevant centre-of-ma ss energy of 240 GeV, near-constant luminosities of 10 34 cms are possible in up to four collision points for a r ing of 27km circumference. The achievable luminosity in creases with the bending radius, and for 80km circumference, a luminosity of 5 10 34 cms in four collision points appears feasible. Beamstra hlung becomes relevant at these high luminosities, leading to a d esign requirement of large momentum acceptance both in the accelerating sys...
This paper describes the TRISTAN control system from the view point of application program develo... more This paper describes the TRISTAN control system from the view point of application program development. The program production started in 1983 and at present 35 man-years have been supplied.
Proceedings of International Conference on Particle Accelerators
An alignment system using stretched wire method [1] is being developed as a component of the acti... more An alignment system using stretched wire method [1] is being developed as a component of the active alignment system for particle accelerator equipment, such as RF cavities and magnets. The RF voltage is supplied to the stretched wire and the monitor measures the change of capacitance between wire and pickup strip from induced charge. Present resolution, limited by the electronics noise, is about 5nm.
A beam test of the multi-bunch energy compensation system (ECS) was performed using the ΔF method... more A beam test of the multi-bunch energy compensation system (ECS) was performed using the ΔF method with the 2856±4.327 MHz accelerating structures in the accelerator test facility (ATF) at KEK. The 1.54 GeV S-band linac of the ATF was designed to accelerate a multi-bunch beam that consists of 20 bunches with 2.8 ns spacing. The multi-bunch beam with 2.0×1010 electrons/bunch has an energy deviation of about 8.5% at the end of the linac due to transient beam loading without ECS. The ATF linac is the injector of the ATF damping ring (DR), whose energy acceptance is ±0.5%. The beam loading compensation system is necessary in the ATF linac for the successful injection of multi-bunch into DR. The rf system of the linac consists of 8 regular rf units with the SLED system and 2 ECS rf units without the SLED system. The accelerating structures of the regular units are driven at 2856 MHz and the 2 ECS structures are operated with slightly different rf frequencies of 2856±4.327 MHz. In the beam...
The KEK NODAL system, which is based on the NODAL devised at the CERN SPS, works on an optical-fi... more The KEK NODAL system, which is based on the NODAL devised at the CERN SPS, works on an optical-fiber token ring network of twenty-four minicomputers (Hitachi HIDIC 80's) to control the TRISTAN accelerator complex, now being constructed at KEK. KEK NODAL retains main features of the original NODAL: the interpreting scheme, the multi-computer programming facility, and the data-module concept. In
Physical Review Special Topics - Accelerators and Beams, 2007
Incoherent emittance growth caused by a strong nonlinear interaction between beam and electron cl... more Incoherent emittance growth caused by a strong nonlinear interaction between beam and electron cloud is discussed. This emittance growth arises from nonlinear diffusion related to chaos and resonances, and strongly depends on the number of degrees of freedom of the interacting system. A simple model, in which beam particles interact with a fixed round charge distribution, is used to study the mechanism of the emittance growth. The same discussion can be applied to the emittance growth due to beam-beam interactions in colliders and space charge effects in low energy proton rings.
In KEKB, synchrotron radiation interferometers (SRMs)[1] are used for measuring the transverse be... more In KEKB, synchrotron radiation interferometers (SRMs)[1] are used for measuring the transverse beam sizes. There is also a tool for enlarging the vertical beam size intentionally by making an asymmetric bump, called an "iSize" bump, at one of the strongest non-interleaved sextupole magnets in each KEKB ring. The calibrations of the SRMs were checked by comparing the measured vertical beam sizes with those calculated using the computer code "SAD". The obtained correction factors are 1.000±0.045 for HER and 0.971±0.060 for LER, which are consistent with the calibration factors of SRMs[2] within errors. Using the obtained calibration factor, the x-y coupling of each ring was calculated .
We report some highlights from the ARIES APEC workshop on "Storage Rings and Gravitational W... more We report some highlights from the ARIES APEC workshop on "Storage Rings and Gravitational Waves" (SRGW2021), held in virtual space from 2 February to 18 March 2021, and sketch a tentative landscape for using accelerators and associated technologies for the detection or generation of gravitational waves.
The FCC-ee Lepton Collider will provide e⁺e⁻ collisions in the beam energy range of 45.6 GeV to 1... more The FCC-ee Lepton Collider will provide e⁺e⁻ collisions in the beam energy range of 45.6 GeV to 182.5 GeV. FCC-ee will be a precision measurement tool for Z, W, H and t physics with expected luminosities of 2.07× 10³⁶ cm⁻² s⁻¹ at the Z-pole and 1.3 × 10³⁴ cm⁻² s⁻¹ at the tt⁻ threshold. In order to achieve the foreseen luminosities, a vertical β^{*} of 1 mm to 2 mm is mandatory. Dynamic aperture and frequency map analysis for the 97.75 km machine with such a squeezed accelerator optics are studied. Furthermore, effects of machine misalignments on dynamic and momentum aperture are presented and estimations for the required tolerances are given
The upgrade of the KEK electron/positron linac for the KEK B-factory project is proceeding. The b... more The upgrade of the KEK electron/positron linac for the KEK B-factory project is proceeding. The beam commissioning of the first 1.5-GeV section of the linac and the 180-degree arc section has been performed. This paper reports on the beam optical matching in the linac and the optical parameter tuning of the arc for the achromatic and isochronous conditions.
To improve collaborative studies on beam dynamics for SuperKEKB between several labs, efforts hav... more To improve collaborative studies on beam dynamics for SuperKEKB between several labs, efforts have been made to translate the SAD lattices of SuperKEKB rings to the versions for other codes: AT, Bmad, MAD-X, and PTC. It turns out that lattice translations between these codes are not straightforward because of the complexity of the SuperKEKB lattices. In this paper, we describe our experiences of lattice translations, and present some results of benchmarks for the case of SuperKEKB.
The 1.54 GeV S-band linac for the Accelerator Test Facility (ATF) accelerates multi-bunch beam. T... more The 1.54 GeV S-band linac for the Accelerator Test Facility (ATF) accelerates multi-bunch beam. The beam has 20 bunches of 2x10 10 electrons with 2.8 ns bunch spacing. When multi-bunch beam is accelerated in the linac, the beam has the energy deviation by transient beam loading. The 1.54 GeV S-band Linac is an injector of the damping ring (DR), and the energy acceptance of the DR is ±0.5%. This means that the beam loading compensation system is necessary in the linac for a successful injection of multi-bunch into DR. The system consists of a compensating section in addition to a regular accelerating section. The accelerating structures of compensating section are operated with slightly different RF frequencies of 2856±4.327MHz. This paper describes the principle of the beam loading compensation system and the results of energy compensating experiment.
The design of the region close to the interaction point of the FCC-ee experiments is especially c... more The design of the region close to the interaction point of the FCC-ee experiments is especially challenging. The beams collide at an angle (+-15 mrad) in the high-field region of the detector solenoid. Moreover, the very low vertical beta_y* of the machine necessitates that the final focusing quadrupoles have a distance from the IP (L*) of around 2 m and therefore are inside the main detector solenoid. The beams should be screened from the effect of the detector magnetic field, and the emittance blow-up due to vertical dispersion in the interaction region should be minimized, while leaving enough space for detector components. Crosstalk between the two final focus quadrupoles, only about 6 cm apart at the tip, should also be minimized.
A crucial part of the design of an FCC-ee detector is the minimisation of the disruption of the b... more A crucial part of the design of an FCC-ee detector is the minimisation of the disruption of the beam due to the presence of a large and powerful detector magnet. Indeed, the emittance blow-up of the few meters around the interaction point (IP) at lower energies is comparable to the emittance introduced by the rest of the 100 km ring. Vertical emittance is the single most important factor in achieving high performance (luminosity, in this case) in a modern e^+ e^- storage ring such as the FCC-ee. The design adopted is the simplest possible arrangement that can nevertheless deliver high performance: two additional coils per IP side. The performance achieved is such that vertical emittance blow-up will not be a limiting performance factor even in the case of a ring with four experiments, and even in the most demanding energy regime, that of the Z running (about 45 GeV beam energy).
We discuss a novel coherent beam-beam instability in collisions with a large crossing angle. The ... more We discuss a novel coherent beam-beam instability in collisions with a large crossing angle. The instability appears in the correlated head-tail motion of the two colliding beams. Cross wake force is introduced to represent the head-tail correlation between colliding beams. The cross wake force is localized at the collision point. Mode coupling theory based on the cross wake force is developed. Collision scheme with a large crossing angle is being very popular in design of electron positron collider. In SuperKEKB project, a collision with a large crossing angle is performed to boost the luminosity 0.8×1036 cm−2s−1. Future circular collider, FCC is also designed with a large crossing angle. Strong-strong simulations have shown a strong coherent head-tail instability, which can limit the performance of proposed future colliders. The mode coupling theory using the cross wake force explains the instability. The instability may affect all colliders designs based on the crab waist scheme.
A strong candidate for the Standard Model Scalar bo son, H(126), has been discovered by the Large... more A strong candidate for the Standard Model Scalar bo son, H(126), has been discovered by the Large Hadro n Collider (LHC) experiments. In order to study this fundamental particle with unprecedented precision, and to perform precision tests of the closure of the Stand ard Model, we investigate the possibilities offered by an ee storage ring collider. We use a design inspired by the B-factori es, taking into account the performance achieved at LEP2, and imposing a synchrotron radiation power limit of 100 MW. At the most relevant centre-of-ma ss energy of 240 GeV, near-constant luminosities of 10 34 cms are possible in up to four collision points for a r ing of 27km circumference. The achievable luminosity in creases with the bending radius, and for 80km circumference, a luminosity of 5 10 34 cms in four collision points appears feasible. Beamstra hlung becomes relevant at these high luminosities, leading to a d esign requirement of large momentum acceptance both in the accelerating sys...
This paper describes the TRISTAN control system from the view point of application program develo... more This paper describes the TRISTAN control system from the view point of application program development. The program production started in 1983 and at present 35 man-years have been supplied.
Proceedings of International Conference on Particle Accelerators
An alignment system using stretched wire method [1] is being developed as a component of the acti... more An alignment system using stretched wire method [1] is being developed as a component of the active alignment system for particle accelerator equipment, such as RF cavities and magnets. The RF voltage is supplied to the stretched wire and the monitor measures the change of capacitance between wire and pickup strip from induced charge. Present resolution, limited by the electronics noise, is about 5nm.
A beam test of the multi-bunch energy compensation system (ECS) was performed using the ΔF method... more A beam test of the multi-bunch energy compensation system (ECS) was performed using the ΔF method with the 2856±4.327 MHz accelerating structures in the accelerator test facility (ATF) at KEK. The 1.54 GeV S-band linac of the ATF was designed to accelerate a multi-bunch beam that consists of 20 bunches with 2.8 ns spacing. The multi-bunch beam with 2.0×1010 electrons/bunch has an energy deviation of about 8.5% at the end of the linac due to transient beam loading without ECS. The ATF linac is the injector of the ATF damping ring (DR), whose energy acceptance is ±0.5%. The beam loading compensation system is necessary in the ATF linac for the successful injection of multi-bunch into DR. The rf system of the linac consists of 8 regular rf units with the SLED system and 2 ECS rf units without the SLED system. The accelerating structures of the regular units are driven at 2856 MHz and the 2 ECS structures are operated with slightly different rf frequencies of 2856±4.327 MHz. In the beam...
The KEK NODAL system, which is based on the NODAL devised at the CERN SPS, works on an optical-fi... more The KEK NODAL system, which is based on the NODAL devised at the CERN SPS, works on an optical-fiber token ring network of twenty-four minicomputers (Hitachi HIDIC 80's) to control the TRISTAN accelerator complex, now being constructed at KEK. KEK NODAL retains main features of the original NODAL: the interpreting scheme, the multi-computer programming facility, and the data-module concept. In
Physical Review Special Topics - Accelerators and Beams, 2007
Incoherent emittance growth caused by a strong nonlinear interaction between beam and electron cl... more Incoherent emittance growth caused by a strong nonlinear interaction between beam and electron cloud is discussed. This emittance growth arises from nonlinear diffusion related to chaos and resonances, and strongly depends on the number of degrees of freedom of the interacting system. A simple model, in which beam particles interact with a fixed round charge distribution, is used to study the mechanism of the emittance growth. The same discussion can be applied to the emittance growth due to beam-beam interactions in colliders and space charge effects in low energy proton rings.
In KEKB, synchrotron radiation interferometers (SRMs)[1] are used for measuring the transverse be... more In KEKB, synchrotron radiation interferometers (SRMs)[1] are used for measuring the transverse beam sizes. There is also a tool for enlarging the vertical beam size intentionally by making an asymmetric bump, called an "iSize" bump, at one of the strongest non-interleaved sextupole magnets in each KEKB ring. The calibrations of the SRMs were checked by comparing the measured vertical beam sizes with those calculated using the computer code "SAD". The obtained correction factors are 1.000±0.045 for HER and 0.971±0.060 for LER, which are consistent with the calibration factors of SRMs[2] within errors. Using the obtained calibration factor, the x-y coupling of each ring was calculated .
We report some highlights from the ARIES APEC workshop on "Storage Rings and Gravitational W... more We report some highlights from the ARIES APEC workshop on "Storage Rings and Gravitational Waves" (SRGW2021), held in virtual space from 2 February to 18 March 2021, and sketch a tentative landscape for using accelerators and associated technologies for the detection or generation of gravitational waves.
The FCC-ee Lepton Collider will provide e⁺e⁻ collisions in the beam energy range of 45.6 GeV to 1... more The FCC-ee Lepton Collider will provide e⁺e⁻ collisions in the beam energy range of 45.6 GeV to 182.5 GeV. FCC-ee will be a precision measurement tool for Z, W, H and t physics with expected luminosities of 2.07× 10³⁶ cm⁻² s⁻¹ at the Z-pole and 1.3 × 10³⁴ cm⁻² s⁻¹ at the tt⁻ threshold. In order to achieve the foreseen luminosities, a vertical β^{*} of 1 mm to 2 mm is mandatory. Dynamic aperture and frequency map analysis for the 97.75 km machine with such a squeezed accelerator optics are studied. Furthermore, effects of machine misalignments on dynamic and momentum aperture are presented and estimations for the required tolerances are given
The upgrade of the KEK electron/positron linac for the KEK B-factory project is proceeding. The b... more The upgrade of the KEK electron/positron linac for the KEK B-factory project is proceeding. The beam commissioning of the first 1.5-GeV section of the linac and the 180-degree arc section has been performed. This paper reports on the beam optical matching in the linac and the optical parameter tuning of the arc for the achromatic and isochronous conditions.
To improve collaborative studies on beam dynamics for SuperKEKB between several labs, efforts hav... more To improve collaborative studies on beam dynamics for SuperKEKB between several labs, efforts have been made to translate the SAD lattices of SuperKEKB rings to the versions for other codes: AT, Bmad, MAD-X, and PTC. It turns out that lattice translations between these codes are not straightforward because of the complexity of the SuperKEKB lattices. In this paper, we describe our experiences of lattice translations, and present some results of benchmarks for the case of SuperKEKB.
The 1.54 GeV S-band linac for the Accelerator Test Facility (ATF) accelerates multi-bunch beam. T... more The 1.54 GeV S-band linac for the Accelerator Test Facility (ATF) accelerates multi-bunch beam. The beam has 20 bunches of 2x10 10 electrons with 2.8 ns bunch spacing. When multi-bunch beam is accelerated in the linac, the beam has the energy deviation by transient beam loading. The 1.54 GeV S-band Linac is an injector of the damping ring (DR), and the energy acceptance of the DR is ±0.5%. This means that the beam loading compensation system is necessary in the linac for a successful injection of multi-bunch into DR. The system consists of a compensating section in addition to a regular accelerating section. The accelerating structures of compensating section are operated with slightly different RF frequencies of 2856±4.327MHz. This paper describes the principle of the beam loading compensation system and the results of energy compensating experiment.
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Papers by K. Oide