| 1. |
- Burkhardt, H., et al.
(författare)
-
Commissioning and Operation at beta = 1000 m in the LHC
- 2013
-
Ingår i: IPAC'13. ; , s. 1983-1984
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We have developed a special optics with aβ∗ of 1000m for two interaction regions (IR1 and IR5) in the LHC, to produce very low divergence beams required for elastic proton-proton scattering. We describe the design, commissioning and operation of this optics in the LHC. Theβ∗ of 1000 m was reached by de-squeezing the beams using 17 intermediate steps beyond the β∗ of 90 m, which had been the previous highest β∗ value reached in the LHC. The optics was measured and the β-beating globally corrected toa level of 10%.
|
|
| 2. |
- Constance, B., et al.
(författare)
-
Experimental Verification of the CLIC Two-Beam Acceleration Technology in CTF3
- 2013
-
Ingår i: IPAC 2013: Proceedings of the 4th International Particle Accelerator Conference. - 9783954501229 ; , s. 1436-1438
-
Konferensbidrag (refereegranskat)abstract
- The Compact Linear Collider international collaboration is pursuing an extensive R&D program towards a multi- TeV electron-positron collider. In particular, the development of two-beam acceleration technology is the focus of the CLIC test facility CTF3. In this paper we summarise the most recent results obtained at CTF3: The results of the studies on the drive beam generation are presented, the achieved two beam acceleration performance is reported and the measured breakdown rates and related observations are summarised. The stability of the deceleration process performed over 12 subsequent modules and a comparison of the obtained results with the theoretical expectations are discussed. We also outline the future experimental program.
|
|
| 3. |
- Dubrovskiy, A., et al.
(författare)
-
Review of the drive beam stabilization in the CLIC test facility CTF3
- 2013
-
Ingår i: IPAC 2013: Proceedings of the 4th International Particle Accelerator Conference. - 9783954501229 ; , s. 2666-2668
-
Konferensbidrag (refereegranskat)abstract
- CTF3 is a Test Facility focusing on beam-based studies of the key concepts of the Compact Linear Collider CLIC. Over the past several years many aspects of the CLIC two-beam acceleration scheme were studied in CTF3, including the crucial issue of drive beam stability. The main sources of drifts and instabilities have been identified and mitigated, helping to improve the machine performance and showing significant progress towards the experimental demonstration of the very stringent requirements on current, energy and phase stability needed in CLIC. In this paper, the more effective techniques and feed-backs are summarized. The latest measurements on beam stability are reported and their relevance to CLIC is discussed.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Persson, Tobias, 1985
(författare)
-
Beam-Based Error Identification and Correction Methods for Particle Accelerators
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modern particle accelerators have tight tolerances on the acceptable deviation from their desired machine parameters. The control of the parameters is of crucial importance for safe machine operation and performance. This thesisfocuses on beam-based methods and algorithms to identify and correct errors in particle accelerators. The optics measurements and corrections of the Large Hadron Collider (LHC), which resulted in an unprecedented low β-beat fora hadron collider is described. The transverse coupling is another parameter which is of importance to control. Improvement in the reconstruction of the coupling from turn-by-turn data has resulted in a significant decrease of the measurement uncertainty. An automatic coupling correction method, which is based on the injected beam oscillations, has been successfully used in normal operation of the LHC. Furthermore, a new method to measure and correct chromatic coupling that was applied to the LHC, is described. It resulted in a decrease of the chromatic coupling by a factor ∼2 for both beams. The good control of the optics is a significant part of the success of the LHC and hence contributed to the discovery of the Higgs particle. Following the discovery of the Higgs particle there is a demand for precise measurements of its properties in a lepton collider. Compact Linear Collider(CLIC), an electron-positron collider aiming at collision energies up to 3 TeV, is one of the leading candidates. The acceleration in CLIC relies on a two-beam acceleration scheme where one of the beams, referred to as the DriveBeam, is decelerated while transferring its energy to the Main Beam. This scheme puts tight constraints on the parameters of the Drive Beam in terms of beam current, phase and bunch length. In CLIC Test Facility 3 (CTF3) themechanisms behind the observed drifts of these parameters have been studied in detail. The findings have shown that these drifts are mainly linked to variations in the amplitude of the Radio Frequency (RF). A feedback to mitigate the RF-amplitude fluctuations has been implemented and is described in detail. In conjunction with a dedicated energy feedback it reduces the energy variation by a factor ∼3. Together with precise machine tuning this has resulted in a beam current stability very close to the CLIC requirement. The beam phase stability is improved through a feedback operating on the two first klystrons in the CTF3 injector. Two-beam acceleration at the nominal CLIC gradient of 100 MV/m and above has been demonstrated in CTF3. These results, and other recent achievements in CTF3, are presented in this thesis.
|
|
| 7. |
- Persson, Tobias, 1985, et al.
(författare)
-
Beam Stability at CTF3
- 2012
-
Ingår i: IPAC 2012 - International Particle Accelerator Conference 2012. - 9783954501151 ; , s. 1888-1890
-
Konferensbidrag (refereegranskat)abstract
- The two-beam acceleration tested at CTF3 imposes verytight tolerances on the drive beam stability. A descriptionof the specialized monitoring tool developed to identify thedrifts and jitter in the machine is presented. It compares all the relevant signals in an on-line manner to help the operator to identify drifts and to log data for off-line analysis. The main sources for the drifts of the drive beam have been identified and their causes are described. A feedback applied to the RF was implemented to reduce the effects. It works by changing the waveform for the pulse compression to compensate for the drifts.
|
|
| 8. |
- Persson, Tobias, 1985, et al.
(författare)
-
Chromatic coupling correction in the Large Hadron Collider
- 2013
-
Ingår i: Physical Review Special Topics - Accelerators and Beams. - 1098-4402. ; 16:8
-
Tidskriftsartikel (refereegranskat)abstract
- In this article we present the measurement and correction of the chromatic coupling in the LHC. The transverse coupling is calculated from turn-by-turn data, exciting the beam with an ac dipole. By adjusting the momentum relative to the reference energy and repeating the measurement, we obtain the transverse coupling dependency on momentum. The measurements are compared to the predictions from the magnetic model, and show good agreement. We describe the algorithm used to calculate the corrections, which are performed using skew sextupoles in the LHC lattice. A reduction in the chromatic coupling of a factor 2.5 +/- 0.4 for beam 1 and 1.6 +/- 0.3 for beam 2 was obtained after applying the corrections.
|
|
| 9. |
- Persson, Tobias, 1985, et al.
(författare)
-
Drive beam stability studies and stabilization algorithms in CLIC Test Facility 3
- 2014
-
Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 735, s. 152-156
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper the study of the mechanisms responsible for the time varying beam current losses in CTF3 (CLIC Test Facility 3), together with the feedbacks implemented to mitigate them, is presented. The study shows that the losses were linked mainly to the energy variation induced by the RF (Radio frequency) amplitude fluctuations. The RF-amplitude instability sources were identified. A feedback developed to mitigate this instability, acting on the RF-compression system by controlling the phase program of the klystron, is described in detail. The result is a significant improvement of the overall stability in the machine. The energy variation is reduced further with the use of an energy feedback operating on the RF-amplitude of the last klystron in the CTF3 linac. This feedback loop closes on the energy measured from a dispersive pickup after the linac. With the energy stabilized a beam current stability close to the CLIC (Compact Linear Collider) specification for a factor 4 combined beam was achieved.
|
|
| 10. |
- Persson, Tobias, 1985, et al.
(författare)
-
Improved control of the betatron coupling in the Large Hadron Collider
- 2014
-
Ingår i: Physical Review Special Topics - Accelerators and Beams. - 1098-4402. ; 17:5
-
Tidskriftsartikel (refereegranskat)abstract
- The control of the betatron coupling is of importance for safe beam operation in the LHC. In this article we show recent advancements in methods and algorithms to measure and correct coupling. The benefit of using a more precise formula relating the resonance driving term f1001 to the ΔQ min is presented. The quality of the coupling measurements is increased, with about a factor 3, by selecting beam position monitor (BPM) pairs with phase advances close to pi/2 and through data cleaning using singular value decomposition with an optimal number of singular values. These improvements are beneficial for the implemented automatic coupling correction, which is based on injection oscillations, presented in the article. Furthermore, a proposed coupling feedback for the LHC is presented. The system will rely on the measurements from BPMs equipped with a new type of high resolution electronics, diode orbit and oscillation, which will be operational when the LHC restarts in 2015. The feedback will combine the coupling measurements from the available BPMs in order to calculate the best correction.
|
|
