48 research outputs found
Dissertatio astronomica de methodo inveniendi latitudinem loci ex observatis duabus solis vel stellae cujusdam altitudinibus. Cujus particulam priorem cons. ampl. facult. philos. Aboëns. praeside mag. Joh. Henr. Lindquist, math. prof. r. [et] o. nec non R. Acad. Scient. Svec. membro. Publice ventilandam sistit Andreas Johannes Mether, stipend. reg. Tavastensis. In auditorio Maj. die XVIII April. MDCCXCII. h. a. m. c.
No full textDedikaatio: Carl Gustaf Mether [ruots. pr.].Painovuosi nimekkeestä.Arkit: 1 arkintunnukseton lehti, A-B4.Piirrosliitteen signeeraus: C. L. Schultz sc.Dedikaatio on ruotsinkielinen
A test on analytic continuation of thermal imaginary-time data
No full textBurnier Y, Laine M, Mether L. A test on analytic continuation of thermal imaginary-time data. European Physical Journal C. 2011;71(4): 1619
Meditationum philologicarum, de pericopa prima capitis decimi Johannis, inprimis voce thyrorô pars posterior; quam, consensu ampliss. facult. philos. in Reg. ad Auram Acad. praeside viro, maxime reverendo atq[ue] celeberrimo d:no Isaaco Ross, s. s. l. l. profess. reg. & ord. Pro gradu, publico examini modeste submittit Henricus H. Alanus, Borea-Fenn. In audit. superiori, die IV. Junii, anno MDCCLXIII. h. a. m. s.
No full textInvokaatio: D.F.G.Dedikaatio: Jacobus Malmsten, Nicolaus Hedeen, Ericus Wallenius, Jonas Dahlgren.Gratulaatio: J. J. Mether [ruots. pr.], C. Sedenius [ransk. pr.].Painovuosi nimekkeestä.Arkit: 2 arkintunnuksetonta lehteä, D-E4 F2.Nimekkeessä on kreikkaa. Ensimmäinen gratulaatio on ruotsinkielinen. Toinen gratulaatio on ranskankielinen
Colour-electric spectral function at next-to-leading order
No full textBurnier Y, Laine M, Langelage J, Mether L. Colour-electric spectral function at next-to-leading order. JHEP. 2010;2010(8): 94.The spectral function related to the correlator of two colour-electric fields along a Polyakov loop determines the momentum diffusion coefficient of a heavy quark near rest with respect to a heat bath. We compute this spectral function at next-to-leading order, O(alpha_s^2), in the weak-coupling expansion. The high-frequency part of our result (omega >> T), which is shown to be temperature-independent, is accurately determined thanks to asymptotic freedom; the low-frequency part of our result (omega 0. We also evaluate the colour-electric Euclidean correlator, which could be directly compared with lattice simulations. As an aside we determine the Euclidean correlator in the lattice strong-coupling expansion, showing that through a limiting procedure it can in principle be defined also in the confined phase of pure Yang-Mills theory, even if a practical measurement could be very noisy there
Electron cloud in the CERN accelerator complex
No full textOperation with closely spaced bunched beams causes the build-up of an Electron Cloud (EC) in both the LHC and the two last synchrotrons of its injector chain (PS and SPS). Pressure rise and beam instabilities are observed at the PS during the last stage of preparation of the LHC beams. The SPS was affected by coherent and incoherent emittance growth along the LHC bunch train over many years, before scrubbing has finally suppressed the EC in a large fraction of the machine. When the LHC started regular operation with 50 ns beams in 2011, EC phenomena appeared in the arcs during the early phases, and in the interaction regions with two beams all along the run. Operation with 25 ns beams (late 2012 and 2015), which is nominal for LHC, has been hampered by EC induced high heat load in the cold arcs, bunch dependent emittance growth and degraded beam lifetime. Dedicated and parasitic machine scrubbing is presently the weapon used at the LHC to combat EC in this mode of operation. This talk summarises the EC experience in the CERN machines (PS, SPS, LHC) and highlights the dangers for future operation with more intense beams as well as the strategies to mitigate or suppress the effect
Dissertatio mathematica, specimina quaedam geometriae curvilineae sistens. Quam cons. ampl. fac. philos. Aboëns. Publico examni subjiciunt mag. Andreas Johannes Mether, math. applic. doc. nec non R. Acad. Bibl. aman. ord. et Nicolaus Israël Berghaell, stip. reg. Tavastenses. In auditorio maj. die 3 Novembr. a. 1798. horis a. m. solitis.
No full textPainovuosi nimekkeestä.Piirrosliite: C. L. S[chultz] sc.Arkit: A-B4. - Sivu [2] ja viimeinen sivu tyhjä
Dissertatio astronomica de usu Stellae polaris ad inveniendum tempus verum. Quam cons. ampl. facult. philos. in Reg. Acad. Aboënsi publico examini subjiciunt Andreas Joh. Mether, phil. mag. et Gustavus Gabriel Hällström, stip. reg. Ostrobotniensis. In auditorio maj. die XVII Dec. a. MDCCXCIV. horis ante meridiem solitis.
No full textDedikaatio: Carol. Nicol. Hellenius.Arkit: 1 arkintunnukseton lehti, A-B4 C2.Painovuosi nimekkeestä.Piirrosliite: C[arolus] L[udovicus] S[chultz] sc
Review of instabilities with ions or/and electrons and possible mitigations
No full textThe presence of ions and electrons from gas ionization, photoemission or secondary emission is unavoidable in the vacuum chambers of high intensity accelerators and storage rings. Under suitable conditions, these ions and electrons can accumulate and drive the beams unstable. In this contribution, the mechanisms behind and the main conditions for ion and electron accumulation in the bunched beams are summarized. The characteristics of the induced instabilities, as well as common modelling techniques and mitigation strategies are reviewed. The possible interplays between ions and electrons are also discussed
Dissertatio astronomica de methodo inveniendi latitudinem loci ex observatis duabus solis vel stellae cujusdam altitudinibus. Cujus particulam posteriorem cons. ampl. fac. philos. Aboëns. praeside mag. Joh. Henr. Lindquist, math. prof. r. [et] o. nec non R. Acad. Scient. Svec. membro. Pro laurea publice ventilandam sistit Andreas Johannes Mether, stipend. reg. Tavastensis. In auditorio minori die XVI Junii an. MDCCXCII. h. a. m. c.
No full textArkit: C-D4.Painovuosi nimekkeestä.Piirrosliitteen signeeraus: C. L. Schultz sculp
Modeling of fast Beam-Ion Instabilities
No full textBeam-induced ionisation of residual gas in the vacuum chamber generates ions, which in an electron machine can accumulate around a passing bunch train. If the density of trapped ions becomes sufficiently high, a fast beam-ion in- stability will be excited. The development of the instability can be prevented by keeping the pressure of the residual gas below a certain value. This contribution describes the mod- eling of fast beam-ion instabilities and presents simulation studies of ion trapping and the evolution of the instability in the FCC-ee. Threshold ion densities for exciting the insta- bility are estimated in order to deduce acceptable vacuum pressures for operation
