Rövid, frekvenciamodulált lézerimpulzus sorozat kölcsönhatása többnívós rendszerekkel = Interaction of a sequence of short frequency-chirped laser pulses with multilevel atoms

Frekvenciamodulált ("csörpölt") rövid lézerimpulzusok és soknívós atomok kölcsönhatását analizáltuk, a 85Rb atom 5S1/2 - 5P3/2 hiperfinom nívói közötti átmeneteit használva elméleti modelként. Fő célkitűzésünk olyan új, hatékony módszerek kifejlesztése, mellyekkel mechanikai impulzust koherensen lehet átadni lézerrel hűtött és magneto-optikai csapdába zárt rubídium atomoknak lézerimpulzusokkal. Rubídium atomnyalábot jó hatásfokkal tudtunk kísérletileg eltéríteni, koherensen gyorsítani és kettéosztani az atomi sokaság számottevő melegedése nélkül, és tanulmányoztuk a lézertérből származó mechanikai momentum atomok számára történő optimális átadásának feltételeit. Az atomi nívók populációjának koherens szabályozására és a rubídium atomok kölcsönhatásban résztvevő nívói közötti koherencia létrehozására új módszert dolgoztunk ki egyetlen frekvenciamodulált lézerimpulzussal, és javasoltunk egy új mechanizmust elektromágnesesen önindukált átlátszóság megvalósítására. Egymással szembehaladó, a kölcsönhatáskor egymást részben átfedő, csörpölt impulzuspárok mechanikai impulzusának atomi sokaságnak történő átadására új mechanizmust dolgoztunk ki elméletileg, és kísérletileg megerősítettük, hogy az impulzusátadás hatásfoka drasztikusan megnövelhető ilyen impulzuspárokkal. | We investigated interaction of frequency modulated (chirped) short laser pulses with multilevel atoms using the hyperfine levels of the 5S1/2-5P3/2 transition in the 85Rb atom as a model for the theoretical analysis. The main goal was to develop new effective schemes for coherent transfer of mechanical momentum from pulsed laser radiation to the Rb atoms previously cooled and trapped in the magneto-optical trap. An effective manipulation of the Rb beam, including deflection, splitting and coherent acceleration of the atomic ensemble without considerable heating of it was experimentally realized and investigated to optimize the efficiency of the mechanical momentum transfer from the laser field to the atoms. Novel schemes of coherent control of the population transfer and generation of coherences between the working levels of the Rb atoms by a single frequency chirped laser pulse were developed and a novel mechanism of the electromagnetically self-induced transparency was proposed. A new mechanism of the mechanical momentum transfer to atomic ensemble from counter-propagating partially overlapping frequency-chirped laser pulses was theoretically predicted and experimentally confirmed that drastically increases the efficiency of the momentum transfer

Kamarai autonómiák Magyarországon és az Európai Unióban - 1990-2004. = Chamber autonomies in Hungary and the European Union between 1990 and 2004

Kutatócsoportunk a kutatás ideje alatt a szakirodalmi és primér forrásállományok feldolgozása mellett aktív kapcsolatokat épített ki külföldi tudományos műhelyekkel, mind a hazai, mind külföldi kamarai vezetőkkel. A pályázat ideje alatt két teljes időben foglalkoztatott doktorandusz és posztdoktor, valamint egy félállásban dolgozó kutató, továbbá egy egyetemi hallgató segítségével végezte munkáját. Az ő segítségükkel került megszervezésre 2007 márciusában egy nemzetközi konferencia, melyen nemcsak munkatársaink, hanem a magyar és nemzetközi kamarai és tudományos élet meghatározó személyiségei is részt vettek. A rendezvényen elhangzott előadások szerkesztett, lábjegyzetelt változatát tanulmánykötetben kiadtuk. "A kamarai tevékenység Magyarországon és az Európai Unióban" című, Gergely Jenő főszerkesztésében, a munkacsoport kutatói által szerkesztett tanulmánykötetben összesen 9 tanulmány, 3 forráspublikáció és egy kerekasztal-beszélgetés lejegyzett szövege, valamint ezek angol és német nyelvű összefoglalása kapott helyet. A kutatás futamidejének végére annak végeredményeként jelent meg a "Gazdasági és szakmai kamarák Magyarországon és az Európai Unióban" címet viselő, több mint háromszáz oldalas záró monográfiánk, valamint a "Kamarák a két világháború között Magyarországon" című, kétszáz oldalas kötetünk is. A tudományos művek használhatóságát növeli, hogy igen terjedelmes angol és német nyelvű rezümét tartalmaznak, illetve CD-ROM változatban is napvilágot láttak. | During the project our research group beside elaborating the sources and scientific literature created lively contacts with foreign scientific workshops, and the leaders of chambers in Hungary and foreign countries. A PhD-student and a PhD working full time, a half time employed researcher and a university student worked in our group. They organized our international conference in March of 2007, where beside our colleagues the important players and experts of Hungarian and foreign chamber and academic life gave lectures. The edited collection of these lectures with footnotes was published in a volume called A kamarai tevékenység Magyarországon és az Európai Unióban (The activity of chambers in Hungary and the European Union). This book edited by Gergely Jenő contains nine studies, three resource-publishing, the text of the scientific debate and its English and German resumes. At the end of our research a book called Gazdasági és szakmai kamarák Magyarországon és az Európai Unióban(Economical and professional chambers in Hungary and the European Union) with more than 300 pages and a monography Kamarák a két világháború között Magyarországon(Chambers of Hungary in the interwar period) with more than 200 pages was published. The utility of these scientific works was increased by the fact that they contain very long English and German abstracts and were published on CD-ROM as well

Stabilization and time resolved measurement of the frequency evolution of a modulated diode laser for chirped pulse generation

We have developed experimental methods for the generation of chirped laser pulses of controlled frequency evolution in the nanosecond pulse length range for coherent atomic interaction studies. The pulses are sliced from the radiation of a cw external cavity diode laser while its drive current, and consequently its frequency, are sinusoidally modulated. By the proper choice of the modulation parameters, as well as of the timing of pulse slicing, we can produce a wide variety of frequency sweep ranges during the pulse. In order to obtain the required frequency chirp, we need to stabilize the center frequency of the modulated laser and to measure the resulting frequency evolution with appropriate temporal resolution. These tasks have been solved by creating a beat signal with a reference laser locked to an atomic transition frequency. The beat signal is then analyzed, as well as its spectral sideband peaks are fed back to the electronics of the frequency stabilization of the modulated laser. This method is simple and it has the possibility for high speed frequency sweep with narrow bandwidth that is appropriate, for example, for selective manipulation of atomic states in a magneto-optical trap

Laser particle acceleration technologies : probe laser beam diagnostics of extended plasmas

As plasma-based particle acceleration techniques are becoming intensely developed, the diagnostic tools for the study of the generation and properties of plasmas are increasingly important. We present results on the investigation of probe laser beam diagnostics for the measurement of the plasma density in extended spatial regions. Such extended plasmas are used in particle driven plasma wakefield acceleration experiments for the acceleration of electron/positron bunches to as high as TeV energies in the foreseeable future

Mid-infrared time-domain study of recent dust production events in the extreme debris disc of TYC 4209-1322-1

Extreme debris discs are characterized by unusually strong mid-infrared excess emission, which often proves to be variable. The warm dust in these discs is of transient nature and is likely related to a recent giant collision occurring close to the star in the terrestrial region. Here we present the results of a 877 days long, gap-free photometric monitoring performed by the Spitzer Space Telescope of the recently discovered extreme debris disc around TYC 4209-1322-1. By combining these observations with other time-domain optical and mid-infrared data, we explore the disc variability of the last four decades, with particular emphasis on the last 12 years. During the latter interval the disc showed substantial changes, the most significant was the brightening and subsequent fading between 2014 and 2018 as outlined in WISE data. The Spitzer light curves outline the fading phase and a subsequent new brightening of the disc after 2018, revealing an additional flux modulation with a period of ~39 days on top of the long-term trend. We found that all these variations can be interpreted as the outcome of a giant collision that happened at an orbital radius of ~0.3 au sometime in 2014. Our analysis implies that a collision on a similar scale could have taken place around 2010, too. The fact that the disc was already peculiarly dust rich 40 years ago, as implied by IRAS data, suggests that these dust production events belong to a chain of large impacts triggered by an earlier even more catastrophic collision

Dipper-like variability of the Gaia alerted young star V555 Ori

V555 Ori is a T Tauri star, whose 1.5 mag brightening was published as a Gaia science alert in 2017. We carried out optical and near-infrared photometric, and optical spectroscopic observations to understand the light variations. The light curves show that V555 Ori was faint before 2017, entered a high state for about a year, and returned to the faint state by mid-2018. In addition to the long-term flux evolution, quasi-periodic brightness oscillations were also evident, with a period of about 5 days. At optical wavelengths both the long-term and short-term variations exhibited colourless changes, while in the near-infrared they were consistent with changing extinction. We explain the brightness variations as the consequence of changing extinction. The object has a low accretion rate whose variation in itself would not be enough to reproduce the optical flux changes. This behaviour makes V555 Ori similar to the pre-main sequence star AA Tau, where the light changes are interpreted as periodic eclipses of the star by a rotating inner disc warp. The brightness maximum of V555 Ori was a moderately obscured ($A_V$=2.3 mag) state, while the extinction in the low state was $A_V$=6.4 mag. We found that while the Gaia alert hinted at an accretion burst, V555 Ori is a standard dipper, similar to the prototype AA Tau. However, unlike in AA Tau, the periodic behaviour was also detectable in the faint phase, implying that the inner disc warp remained stable in both the high and low states of the system.Comment: Accepted to MNRA

Phototherapy-induced blistering reaction and eruptive melanocytic nevi in a child with transient neonatal porphyrinemia

Neonatal blue-light phototherapy induced a blistering reaction followed by eruption of melanocytic nevi on the exposed skin surface of a child with transient neonatal porphyrinemia. New nevi are still developing 4 years after the triggering event. The role of phototoxicity-induced epidermal injury, that of porphyrins and the influence of neonatal blue-light therapy, in this unique phenomenon are discussed

Pre-excitation studies for rubidium-plasma generation

The key element in the Proton-Driven-Plasma-Wake-Field-Accelerator (AWAKE) project is the generation of highly uniform plasma from Rubidium vapor. The standard way to achieve full ionization is to use high power laser which can assure the over-barrier-ionization (OBI) along the 10 meters long active region. The Wigner-team in Budapest is investigating an alternative way of uniform plasma generation. The proposed Resonance Enhanced Multi Photon Ionization (REMPI) scheme probably can be realized by much less laser power. In the following the resonant pre-excitations of the Rb atoms are investigated, theoretically and the status report about the preparatory work on the experiment are presented