{"id":4359,"date":"2026-02-11T00:19:29","date_gmt":"2026-02-10T23:19:29","guid":{"rendered":"https:\/\/www.swissrocketman.fr\/Wordpress\/?p=4359"},"modified":"2026-02-12T15:53:27","modified_gmt":"2026-02-12T14:53:27","slug":"beam-catcher","status":"publish","type":"post","link":"https:\/\/www.swissrocketman.fr\/Wordpress\/?p=4359","title":{"rendered":"beam catcher (ou beam dump extr\u00eame), con\u00e7u pour arr\u00eater des pulses laser mega et terrawatts"},"content":{"rendered":"

beam catcher<\/strong> (ou beam dump<\/em> extr\u00eame), con\u00e7u non pas pour absorber gentiment\u2026 mais pour survivre \u00e0 un tir catastrophique<\/strong>.<\/h2>\n<\/div><\/section><\/div>\n
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https:\/\/chatgpt.com\/share\/698bc0c3-7aa0-8000-9b51-d4dd650e5034<\/span><\/a><\/h3>\n<\/div><\/section><\/div>\n
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c’est un \u00ab\u00a0beam catcher\u00a0\u00bb il est capable d’arr\u00eater des faisceaux lasers ultra intense. Peux tu me d\u00e9crire son principe de fonctionnement lorsqu’un faisceau de 5 TW en 1 picoseconde frappe celui-ci .<\/div>\n
beam catcher<\/strong> (ou beam dump<\/em> extr\u00eame), con\u00e7u non pas pour absorber gentiment\u2026 mais pour survivre \u00e0 un tir catastrophique<\/strong>.<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/article>\n
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Je te d\u00e9cris pas \u00e0 pas<\/strong> ce qui se passe quand 5 TW \u2013 1 ps<\/strong> frappent cet objet pr\u00e9cis<\/strong>.<\/p>\n

Donn\u00e9es du tir (ordre de grandeur)<\/p>\n

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    Puissance cr\u00eate : 5 TW<\/strong><\/p>\n<\/li>\n

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    Dur\u00e9e : 1 ps<\/strong><\/p>\n<\/li>\n

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    \u00c9nergie totale :<\/p>\n

    E=P\u00d7t=5\u00d71012\u00d710\u221212=5\u00a0JE = P \\times t = 5\\times10^{12} \\times 10^{-12} = \\mathbf{5\\ J}<\/span>E<\/span>=<\/span><\/span>P<\/span>\u00d7<\/span><\/span>t<\/span>=<\/span><\/span>5<\/span>\u00d7<\/span><\/span>1<\/span>012<\/span><\/span><\/span><\/span><\/span><\/span><\/span>\u00d7<\/span><\/span>1<\/span>0\u221212<\/span><\/span><\/span><\/span><\/span><\/span><\/span>=<\/span><\/span>5<\/span>\u00a0<\/span>J<\/span><\/span><\/span><\/span><\/span><\/span><\/li>\n

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    Focalisation typique accidentelle :
    spot ~ 10\u201350 \u00b5m<\/strong> (parfois pire\u2026)<\/p>\n<\/li>\n<\/ul>\n

    \ud83d\udc49 On est bien au-del\u00e0<\/strong> :<\/p>\n

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      seuil d\u2019ablation<\/p>\n<\/li>\n

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      seuil plasma<\/p>\n<\/li>\n

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      seuil de fusion<\/p>\n<\/li>\n

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      seuil de choc thermique<\/p>\n<\/li>\n<\/ul>\n

      Principe fondamental du beam catcher<\/h2>\n
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      Il ne cherche PAS \u00e0 absorber l\u2019\u00e9nergie.
      Il cherche \u00e0 la rendre inoffensive le plus vite possible.<\/strong><\/p>\n<\/blockquote>\n

      C\u2019est une diff\u00e9rence cl\u00e9.<\/p>\n

      S\u00e9quence physique r\u00e9elle (picoseconde par picoseconde)<\/p>\n

      \u23f1\ufe0f t = 0 \u2192 50 fs<\/h3>\n

      Interaction \u00e9lectrons libres<\/strong><\/p>\n

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        Le champ optique est colossal<\/p>\n<\/li>\n

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        Ionisation multiphotonique imm\u00e9diate<\/p>\n<\/li>\n

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        Les \u00e9lectrons deviennent quasi libres<\/p>\n<\/li>\n

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        Le m\u00e9tal cesse d\u2019\u00eatre un solide optique<\/strong><\/p>\n<\/li>\n<\/ul>\n

        \u27a1\ufe0f Le mat\u00e9riau devient plasma dense<\/strong> avant tout \u00e9chauffement macroscopique.<\/p>\n

        \u23f1\ufe0f t = 50 fs \u2192 500 fs<\/h3>\n

        Formation d\u2019un plasma opaque<\/strong><\/p>\n

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          La surface cuivre \/ pointe \u00e9met un plasma<\/p>\n<\/li>\n

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          Densit\u00e9 \u00e9lectronique > densit\u00e9 critique<\/p>\n<\/li>\n

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          Le plasma devient r\u00e9fl\u00e9chissant \/ diffusant<\/strong><\/p>\n<\/li>\n<\/ul>\n

          \ud83d\udc49 Le reste de l\u2019impulsion ne p\u00e9n\u00e8tre plus<\/strong>.<\/p>\n

          C\u2019est le point cl\u00e9 :<\/p>\n

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          le beam catcher se prot\u00e8ge lui-m\u00eame en devenant opaque.<\/strong><\/p>\n<\/blockquote>\n

          \u23f1\ufe0f t \u2248 1 ps (fin de l\u2019impulsion)<\/h3>\n
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            L\u2019\u00e9nergie n\u2019a p\u00e9n\u00e9tr\u00e9 que sur :<\/p>\n

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              quelques dizaines de nm<\/strong><\/p>\n<\/li>\n<\/ul>\n<\/li>\n

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              Le volume affect\u00e9 est microscopique<\/strong><\/p>\n<\/li>\n

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              Aucune conduction thermique possible (temps trop court)<\/p>\n<\/li>\n<\/ul>\n

              \u27a1\ufe0f Pas de propagation de d\u00e9g\u00e2ts.<\/p>\n

              Pourquoi la g\u00e9om\u00e9trie est cruciale<\/p>\n

              \ud83d\udd3a Pointe centrale<\/h3>\n
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                Champ renforc\u00e9 localement<\/p>\n<\/li>\n

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                Plasma initi\u00e9 au centre<\/strong>, pas sur les parois<\/p>\n<\/li>\n

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                Pas de r\u00e9flexion sp\u00e9culaire dangereuse<\/p>\n<\/li>\n

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                Diffusion conique vers l\u2019int\u00e9rieur du tube<\/p>\n<\/li>\n<\/ul>\n

                \ud83d\udfeb Tube cuivre \u00e9pais<\/h3>\n
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                  Grande masse thermique<\/p>\n<\/li>\n

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                  Tr\u00e8s haute conductivit\u00e9<\/p>\n<\/li>\n

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                  Supporte l\u2019onde de choc locale<\/p>\n<\/li>\n

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                  \u00c9vite toute sortie arri\u00e8re<\/p>\n<\/li>\n<\/ul>\n

                  \u26ab Support isolant<\/h3>\n
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                    Aucun arc<\/p>\n<\/li>\n

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                    Pas de chemin parasite<\/p>\n<\/li>\n

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                    M\u00e9caniquement stable apr\u00e8s choc<\/p>\n<\/li>\n

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                    Ce qu\u2019il FAIT r\u00e9ellement au faisceau<\/span><\/p>\n<\/li>\n<\/ul>\n

                    Il combine 4 m\u00e9canismes simultan\u00e9s<\/strong> :<\/p>\n

                    1\ufe0f\u20e3 Plasma shielding<\/strong>
                    \u2192 le faisceau s\u2019\u00e9teint sur son propre plasma<\/p>\n

                    2\ufe0f\u20e3 Diffusion angulaire<\/strong>
                    \u2192 l\u2019\u00e9nergie est r\u00e9partie dans le volume interne<\/p>\n

                    3\ufe0f\u20e3 Ablation sacrificielle localis\u00e9e<\/strong>
                    \u2192 quelques \u00b5g de mati\u00e8re disparaissent, pas plus<\/p>\n

                    4\ufe0f\u20e3 Pas de r\u00e9flexion coh\u00e9rente<\/strong>
                    \u2192 aucune r\u00e9tro-propagation destructrice<\/p>\n

                    Pourquoi il peut \u201carr\u00eater\u201d 5 TW<\/h2>\n

                    Parce que :<\/p>\n

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                      5 J<\/strong>, ce n\u2019est PAS \u00e9norme en \u00e9nergie<\/p>\n<\/li>\n

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                      1 ps<\/strong>, c\u2019est trop court pour d\u00e9truire un volume<\/p>\n<\/li>\n

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                      Le plasma se forme avant que le mat\u00e9riau ne souffre<\/strong><\/p>\n<\/li>\n<\/ul>\n

                      \ud83d\udc49 On d\u00e9truit la surface<\/strong>, pas l\u2019objet.<\/p>\n

                      Apr\u00e8s le tir : que reste-t-il ?<\/h2>\n
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                        Une micro-crat\u00e9risation interne<\/p>\n<\/li>\n

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                        Un d\u00e9p\u00f4t de suie\/plasma condens\u00e9<\/p>\n<\/li>\n

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                        L\u2019optique en amont est sauv\u00e9e<\/strong><\/p>\n<\/li>\n

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                        Le beam catcher reste fonctionnel (souvent plusieurs tirs)<\/p>\n<\/li>\n<\/ul>\n

                        C\u2019est exactement ce qu\u2019on lui demande.<\/p>\n

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                        Un beam catcher arr\u00eate un faisceau TW non pas en l\u2019absorbant, mais en le for\u00e7ant \u00e0 s\u2019auto-\u00e9teindre dans un plasma qu\u2019il g\u00e9n\u00e8re lui-m\u00eame.<\/strong><\/span><\/h2>\n<\/blockquote>\n

                        Tr\u00e8s belle pi\u00e8ce. Et tr\u00e8s bon \u0153il \ud83d\udc40\ud83d\udd25<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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                        1\ufe0f\u20e3 Fluence maximale tol\u00e9rable (ordre de grandeur r\u00e9aliste)<\/span><\/p>\n

                        On raisonne au seuil o\u00f9 le mat\u00e9riau n\u2019a plus le temps de \u201cchauffer\u201d<\/strong>, mais passe directement en plasma r\u00e9fl\u00e9chissant<\/strong>.<\/p>\n

                        Param\u00e8tres typiques<\/h3>\n
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                          Mat\u00e9riau : Cuivre \/ tungst\u00e8ne (pointe)<\/strong><\/p>\n<\/li>\n

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                          Dur\u00e9e d\u2019impulsion : fs\u2013ps<\/strong><\/p>\n<\/li>\n

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                          R\u00e9gime : ionisation ultrarapide<\/strong><\/p>\n<\/li>\n<\/ul>\n

                          Seuils connus (exp\u00e9rimental)<\/h3>\n
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                          Dur\u00e9e<\/th>\nSeuil plasma m\u00e9tal<\/th>\n<\/tr>\n<\/thead>\n
                          1 ps<\/td>\n~1\u20135 J\/cm\u00b2<\/strong><\/td>\n<\/tr>\n
                          100 fs<\/td>\n~0.1\u20130.5 J\/cm\u00b2<\/strong><\/td>\n<\/tr>\n
                          30 fs<\/td>\n~0.02\u20130.1 J\/cm\u00b2<\/strong><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n

                          \ud83d\udc49 Au-dessus de ces fluences<\/strong>, la surface devient plasma avant<\/strong> diffusion thermique.<\/p>\n

                          Pour ton beam catcher<\/h3>\n
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                            Il est con\u00e7u pour :<\/p>\n

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                              d\u00e9clencher le plasma au centre<\/strong><\/p>\n<\/li>\n

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                              \u00e9viter toute r\u00e9flexion coh\u00e9rente<\/p>\n<\/li>\n<\/ul>\n<\/li>\n

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                              La fluence \u201ctol\u00e9rable\u201d n\u2019est pas l\u2019absorption, mais :<\/p>\n<\/li>\n<\/ul>\n

                              jusqu\u2019a\u02cb\u00a0\u223c10\u00a0J\/cm2\u00a0en\u00a0ps,\u00a0car\u00a0le\u00a0plasma\u00a0coupe\u00a0l\u2019interaction\\boxed{\\text{jusqu\u2019\u00e0 } \\sim 10\\ \\mathrm{J\/cm^2}\\ \\text{en ps, car le plasma coupe l\u2019interaction}}<\/span>jusqu\u2019a\u02cb<\/span><\/span><\/span>\u00a0<\/span>\u223c<\/span>10\u00a0<\/span>J\/c<\/span>m<\/span>2<\/span><\/span><\/span><\/span>\u00a0<\/span>en\u00a0ps,\u00a0car\u00a0le\u00a0plasma\u00a0coupe\u00a0l\u2019interaction<\/span><\/span><\/span>\u200b<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/p>\n

                              \u27a1\ufe0f La limite r\u00e9elle est m\u00e9canique (\u00e9rosion cumulative)<\/strong>, pas instantan\u00e9e<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/article>\n<\/div><\/section><\/div>

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